Revert "libpng 1.6.3"

third_party/libpng/pngrtran.c

 
 /* pngrtran.c - transforms the data in a row for PNG readers
  *
- * Last changed in libpng 1.6.2 [April 25, 2013]
- * Copyright (c) 1998-2013 Glenn Randers-Pehrson
+ * Last changed in libpng 1.2.45 [July 7, 2011]
+ * Copyright (c) 1998-2011 Glenn Randers-Pehrson
  * (Version 0.96 Copyright (c) 1996, 1997 Andreas Dilger)
  * (Version 0.88 Copyright (c) 1995, 1996 Guy Eric Schalnat, Group 42, Inc.)
  *
  * This code is released under the libpng license.
  * For conditions of distribution and use, see the disclaimer
  * and license in png.h
  *
  * This file contains functions optionally called by an application
  * in order to tell libpng how to handle data when reading a PNG.
  * Transformations that are used in both reading and writing are
  * in pngtrans.c.
  */
 
-#include "pngpriv.h"
-
+#define PNG_INTERNAL
+#define PNG_NO_PEDANTIC_WARNINGS
+#include "png.h"
 #ifdef PNG_READ_SUPPORTED
 
 /* Set the action on getting a CRC error for an ancillary or critical chunk. */
 void PNGAPI
-png_set_crc_action(png_structrp png_ptr, int crit_action, int ancil_action)
+png_set_crc_action(png_structp png_ptr, int crit_action, int ancil_action)
 {
    png_debug(1, "in png_set_crc_action");
-
+ 
    if (png_ptr == NULL)
       return;
 
    /* Tell libpng how we react to CRC errors in critical chunks */
    switch (crit_action)
    {
       case PNG_CRC_NO_CHANGE:                        /* Leave setting as is */
          break;
 
       case PNG_CRC_WARN_USE:                               /* Warn/use data */
          png_ptr->flags &= ~PNG_FLAG_CRC_CRITICAL_MASK;
          png_ptr->flags |= PNG_FLAG_CRC_CRITICAL_USE;
          break;
 
       case PNG_CRC_QUIET_USE:                             /* Quiet/use data */
          png_ptr->flags &= ~PNG_FLAG_CRC_CRITICAL_MASK;
          png_ptr->flags |= PNG_FLAG_CRC_CRITICAL_USE |
                            PNG_FLAG_CRC_CRITICAL_IGNORE;
          break;
 
       case PNG_CRC_WARN_DISCARD:    /* Not a valid action for critical data */
          png_warning(png_ptr,
-            "Can't discard critical data on CRC error");
+            "Can't discard critical data on CRC error.");
       case PNG_CRC_ERROR_QUIT:                                /* Error/quit */
 
       case PNG_CRC_DEFAULT:
       default:
          png_ptr->flags &= ~PNG_FLAG_CRC_CRITICAL_MASK;
          break;
    }
 
    /* Tell libpng how we react to CRC errors in ancillary chunks */
    switch (ancil_action)
@@ skipping 19 matching lines @@
 
       case PNG_CRC_WARN_DISCARD:                      /* Warn/discard data */
 
       case PNG_CRC_DEFAULT:
       default:
          png_ptr->flags &= ~PNG_FLAG_CRC_ANCILLARY_MASK;
          break;
    }
 }
 
-#ifdef PNG_READ_TRANSFORMS_SUPPORTED
-/* Is it OK to set a transformation now?  Only if png_start_read_image or
- * png_read_update_info have not been called.  It is not necessary for the IHDR
- * to have been read in all cases, the parameter allows for this check too.
- */
-static int
-png_rtran_ok(png_structrp png_ptr, int need_IHDR)
+#if defined(PNG_READ_BACKGROUND_SUPPORTED) && \
+    defined(PNG_FLOATING_POINT_SUPPORTED)
+/* Handle alpha and tRNS via a background color */
+void PNGAPI
+png_set_background(png_structp png_ptr,
+   png_color_16p background_color, int background_gamma_code,
+   int need_expand, double background_gamma)
 {
-   if (png_ptr != NULL)
-   {
-      if (png_ptr->flags & PNG_FLAG_ROW_INIT)
-         png_app_error(png_ptr,
-            "invalid after png_start_read_image or png_read_update_info");
-
-      else if (need_IHDR && (png_ptr->mode & PNG_HAVE_IHDR) == 0)
-         png_app_error(png_ptr, "invalid before the PNG header has been read");
-
-      else
-      {
-         /* Turn on failure to initialize correctly for all transforms. */
-         png_ptr->flags |= PNG_FLAG_DETECT_UNINITIALIZED;
-
-         return 1; /* Ok */
-      }
-   }
-
-   return 0; /* no png_error possible! */
-}
-#endif
-
-#ifdef PNG_READ_BACKGROUND_SUPPORTED
-/* Handle alpha and tRNS via a background color */
-void PNGFAPI
-png_set_background_fixed(png_structrp png_ptr,
-    png_const_color_16p background_color, int background_gamma_code,
-    int need_expand, png_fixed_point background_gamma)
-{
-   png_debug(1, "in png_set_background_fixed");
-
-   if (!png_rtran_ok(png_ptr, 0) || background_color == NULL)
+   png_debug(1, "in png_set_background");
+ 
+   if (png_ptr == NULL)
       return;
-
    if (background_gamma_code == PNG_BACKGROUND_GAMMA_UNKNOWN)
    {
       png_warning(png_ptr, "Application must supply a known background gamma");
       return;
    }
 
-   png_ptr->transformations |= PNG_COMPOSE | PNG_STRIP_ALPHA;
-   png_ptr->transformations &= ~PNG_ENCODE_ALPHA;
-   png_ptr->flags &= ~PNG_FLAG_OPTIMIZE_ALPHA;
-
-   png_ptr->background = *background_color;
-   png_ptr->background_gamma = background_gamma;
+   png_ptr->transformations |= PNG_BACKGROUND;
+   png_memcpy(&(png_ptr->background), background_color,
+      png_sizeof(png_color_16));
+   png_ptr->background_gamma = (float)background_gamma;
    png_ptr->background_gamma_type = (png_byte)(background_gamma_code);
-   if (need_expand)
-      png_ptr->transformations |= PNG_BACKGROUND_EXPAND;
-   else
-      png_ptr->transformations &= ~PNG_BACKGROUND_EXPAND;
-}
-
-#  ifdef PNG_FLOATING_POINT_SUPPORTED
-void PNGAPI
-png_set_background(png_structrp png_ptr,
-    png_const_color_16p background_color, int background_gamma_code,
-    int need_expand, double background_gamma)
-{
-   png_set_background_fixed(png_ptr, background_color, background_gamma_code,
-      need_expand, png_fixed(png_ptr, background_gamma, "png_set_background"));
-}
-#  endif  /* FLOATING_POINT */
-#endif /* READ_BACKGROUND */
-
-/* Scale 16-bit depth files to 8-bit depth.  If both of these are set then the
- * one that pngrtran does first (scale) happens.  This is necessary to allow the
- * TRANSFORM and API behavior to be somewhat consistent, and it's simpler.
- */
-#ifdef PNG_READ_SCALE_16_TO_8_SUPPORTED
-void PNGAPI
-png_set_scale_16(png_structrp png_ptr)
-{
-   png_debug(1, "in png_set_scale_16");
-
-   if (!png_rtran_ok(png_ptr, 0))
-      return;
-
-   png_ptr->transformations |= PNG_SCALE_16_TO_8;
+   png_ptr->transformations |= (need_expand ? PNG_BACKGROUND_EXPAND : 0);
 }
 #endif
 
-#ifdef PNG_READ_STRIP_16_TO_8_SUPPORTED
-/* Chop 16-bit depth files to 8-bit depth */
+#ifdef PNG_READ_16_TO_8_SUPPORTED
+/* Strip 16 bit depth files to 8 bit depth */
 void PNGAPI
-png_set_strip_16(png_structrp png_ptr)
+png_set_strip_16(png_structp png_ptr)
 {
    png_debug(1, "in png_set_strip_16");
 
-   if (!png_rtran_ok(png_ptr, 0))
+   if (png_ptr == NULL)
       return;
-
    png_ptr->transformations |= PNG_16_TO_8;
 }
 #endif
 
 #ifdef PNG_READ_STRIP_ALPHA_SUPPORTED
 void PNGAPI
-png_set_strip_alpha(png_structrp png_ptr)
+png_set_strip_alpha(png_structp png_ptr)
 {
    png_debug(1, "in png_set_strip_alpha");
 
-   if (!png_rtran_ok(png_ptr, 0))
+   if (png_ptr == NULL)
       return;
-
-   png_ptr->transformations |= PNG_STRIP_ALPHA;
+   png_ptr->flags |= PNG_FLAG_STRIP_ALPHA;
 }
 #endif
 
-#if defined(PNG_READ_ALPHA_MODE_SUPPORTED) || defined(PNG_READ_GAMMA_SUPPORTED)
-static png_fixed_point
-translate_gamma_flags(png_structrp png_ptr, png_fixed_point output_gamma,
-   int is_screen)
-{
-   /* Check for flag values.  The main reason for having the old Mac value as a
-    * flag is that it is pretty near impossible to work out what the correct
-    * value is from Apple documentation - a working Mac system is needed to
-    * discover the value!
-    */
-   if (output_gamma == PNG_DEFAULT_sRGB ||
-      output_gamma == PNG_FP_1 / PNG_DEFAULT_sRGB)
-   {
-      /* If there is no sRGB support this just sets the gamma to the standard
-       * sRGB value.  (This is a side effect of using this function!)
-       */
-#     ifdef PNG_READ_sRGB_SUPPORTED
-         png_ptr->flags |= PNG_FLAG_ASSUME_sRGB;
-#     else
-         PNG_UNUSED(png_ptr)
-#     endif
-      if (is_screen)
-         output_gamma = PNG_GAMMA_sRGB;
-      else
-         output_gamma = PNG_GAMMA_sRGB_INVERSE;
-   }
-
-   else if (output_gamma == PNG_GAMMA_MAC_18 ||
-      output_gamma == PNG_FP_1 / PNG_GAMMA_MAC_18)
-   {
-      if (is_screen)
-         output_gamma = PNG_GAMMA_MAC_OLD;
-      else
-         output_gamma = PNG_GAMMA_MAC_INVERSE;
-   }
-
-   return output_gamma;
-}
-
-#  ifdef PNG_FLOATING_POINT_SUPPORTED
-static png_fixed_point
-convert_gamma_value(png_structrp png_ptr, double output_gamma)
-{
-   /* The following silently ignores cases where fixed point (times 100,000)
-    * gamma values are passed to the floating point API.  This is safe and it
-    * means the fixed point constants work just fine with the floating point
-    * API.  The alternative would just lead to undetected errors and spurious
-    * bug reports.  Negative values fail inside the _fixed API unless they
-    * correspond to the flag values.
-    */
-   if (output_gamma > 0 && output_gamma < 128)
-      output_gamma *= PNG_FP_1;
-
-   /* This preserves -1 and -2 exactly: */
-   output_gamma = floor(output_gamma + .5);
-
-   if (output_gamma > PNG_FP_MAX || output_gamma < PNG_FP_MIN)
-      png_fixed_error(png_ptr, "gamma value");
-
-   return (png_fixed_point)output_gamma;
-}
-#  endif
-#endif /* READ_ALPHA_MODE || READ_GAMMA */
-
-#ifdef PNG_READ_ALPHA_MODE_SUPPORTED
-void PNGFAPI
-png_set_alpha_mode_fixed(png_structrp png_ptr, int mode,
-   png_fixed_point output_gamma)
-{
-   int compose = 0;
-   png_fixed_point file_gamma;
-
-   png_debug(1, "in png_set_alpha_mode");
-
-   if (!png_rtran_ok(png_ptr, 0))
-      return;
-
-   output_gamma = translate_gamma_flags(png_ptr, output_gamma, 1/*screen*/);
-
-   /* Validate the value to ensure it is in a reasonable range. The value
-    * is expected to be 1 or greater, but this range test allows for some
-    * viewing correction values.  The intent is to weed out users of this API
-    * who use the inverse of the gamma value accidentally!  Since some of these
-    * values are reasonable this may have to be changed.
-    */
-   if (output_gamma < 70000 || output_gamma > 300000)
-      png_error(png_ptr, "output gamma out of expected range");
-
-   /* The default file gamma is the inverse of the output gamma; the output
-    * gamma may be changed below so get the file value first:
-    */
-   file_gamma = png_reciprocal(output_gamma);
-
-   /* There are really 8 possibilities here, composed of any combination
-    * of:
-    *
-    *    premultiply the color channels
-    *    do not encode non-opaque pixels
-    *    encode the alpha as well as the color channels
-    *
-    * The differences disappear if the input/output ('screen') gamma is 1.0,
-    * because then the encoding is a no-op and there is only the choice of
-    * premultiplying the color channels or not.
-    *
-    * png_set_alpha_mode and png_set_background interact because both use
-    * png_compose to do the work.  Calling both is only useful when
-    * png_set_alpha_mode is used to set the default mode - PNG_ALPHA_PNG - along
-    * with a default gamma value.  Otherwise PNG_COMPOSE must not be set.
-    */
-   switch (mode)
-   {
-      case PNG_ALPHA_PNG:        /* default: png standard */
-         /* No compose, but it may be set by png_set_background! */
-         png_ptr->transformations &= ~PNG_ENCODE_ALPHA;
-         png_ptr->flags &= ~PNG_FLAG_OPTIMIZE_ALPHA;
-         break;
-
-      case PNG_ALPHA_ASSOCIATED: /* color channels premultiplied */
-         compose = 1;
-         png_ptr->transformations &= ~PNG_ENCODE_ALPHA;
-         png_ptr->flags &= ~PNG_FLAG_OPTIMIZE_ALPHA;
-         /* The output is linear: */
-         output_gamma = PNG_FP_1;
-         break;
-
-      case PNG_ALPHA_OPTIMIZED:  /* associated, non-opaque pixels linear */
-         compose = 1;
-         png_ptr->transformations &= ~PNG_ENCODE_ALPHA;
-         png_ptr->flags |= PNG_FLAG_OPTIMIZE_ALPHA;
-         /* output_gamma records the encoding of opaque pixels! */
-         break;
-
-      case PNG_ALPHA_BROKEN:     /* associated, non-linear, alpha encoded */
-         compose = 1;
-         png_ptr->transformations |= PNG_ENCODE_ALPHA;
-         png_ptr->flags &= ~PNG_FLAG_OPTIMIZE_ALPHA;
-         break;
-
-      default:
-         png_error(png_ptr, "invalid alpha mode");
-   }
-
-   /* Only set the default gamma if the file gamma has not been set (this has
-    * the side effect that the gamma in a second call to png_set_alpha_mode will
-    * be ignored.)
-    */
-   if (png_ptr->colorspace.gamma == 0)
-   {
-      png_ptr->colorspace.gamma = file_gamma;
-      png_ptr->colorspace.flags |= PNG_COLORSPACE_HAVE_GAMMA;
-   }
-
-   /* But always set the output gamma: */
-   png_ptr->screen_gamma = output_gamma;
-
-   /* Finally, if pre-multiplying, set the background fields to achieve the
-    * desired result.
-    */
-   if (compose)
-   {
-      /* And obtain alpha pre-multiplication by composing on black: */
-      memset(&png_ptr->background, 0, (sizeof png_ptr->background));
-      png_ptr->background_gamma = png_ptr->colorspace.gamma; /* just in case */
-      png_ptr->background_gamma_type = PNG_BACKGROUND_GAMMA_FILE;
-      png_ptr->transformations &= ~PNG_BACKGROUND_EXPAND;
-
-      if (png_ptr->transformations & PNG_COMPOSE)
-         png_error(png_ptr,
-            "conflicting calls to set alpha mode and background");
-
-      png_ptr->transformations |= PNG_COMPOSE;
-   }
-}
-
-#  ifdef PNG_FLOATING_POINT_SUPPORTED
-void PNGAPI
-png_set_alpha_mode(png_structrp png_ptr, int mode, double output_gamma)
-{
-   png_set_alpha_mode_fixed(png_ptr, mode, convert_gamma_value(png_ptr,
-      output_gamma));
-}
-#  endif
-#endif
-
-#ifdef PNG_READ_QUANTIZE_SUPPORTED
-/* Dither file to 8-bit.  Supply a palette, the current number
+#ifdef PNG_READ_DITHER_SUPPORTED
+/* Dither file to 8 bit.  Supply a palette, the current number
  * of elements in the palette, the maximum number of elements
  * allowed, and a histogram if possible.  If the current number
  * of colors is greater then the maximum number, the palette will be
- * modified to fit in the maximum number.  "full_quantize" indicates
- * whether we need a quantizing cube set up for RGB images, or if we
+ * modified to fit in the maximum number.  "full_dither" indicates
+ * whether we need a dithering cube set up for RGB images, or if we
  * simply are reducing the number of colors in a paletted image.
  */
 
 typedef struct png_dsort_struct
 {
-   struct png_dsort_struct * next;
+   struct png_dsort_struct FAR * next;
    png_byte left;
    png_byte right;
 } png_dsort;
-typedef png_dsort *   png_dsortp;
-typedef png_dsort * * png_dsortpp;
+typedef png_dsort FAR *       png_dsortp;
+typedef png_dsort FAR * FAR * png_dsortpp;
 
 void PNGAPI
-png_set_quantize(png_structrp png_ptr, png_colorp palette,
-    int num_palette, int maximum_colors, png_const_uint_16p histogram,
-    int full_quantize)
+png_set_dither(png_structp png_ptr, png_colorp palette,
+   int num_palette, int maximum_colors, png_uint_16p histogram,
+   int full_dither)
 {
-   png_debug(1, "in png_set_quantize");
+   png_debug(1, "in png_set_dither");
 
-   if (!png_rtran_ok(png_ptr, 0))
+   if (png_ptr == NULL)
       return;
+   png_ptr->transformations |= PNG_DITHER;
 
-   png_ptr->transformations |= PNG_QUANTIZE;
-
-   if (!full_quantize)
+   if (!full_dither)
    {
       int i;
 
-      png_ptr->quantize_index = (png_bytep)png_malloc(png_ptr,
-          (png_uint_32)(num_palette * (sizeof (png_byte))));
+      png_ptr->dither_index = (png_bytep)png_malloc(png_ptr,
+         (png_uint_32)(num_palette * png_sizeof(png_byte)));
       for (i = 0; i < num_palette; i++)
-         png_ptr->quantize_index[i] = (png_byte)i;
+         png_ptr->dither_index[i] = (png_byte)i;
    }
 
    if (num_palette > maximum_colors)
    {
       if (histogram != NULL)
       {
          /* This is easy enough, just throw out the least used colors.
           * Perhaps not the best solution, but good enough.
           */
 
          int i;
 
          /* Initialize an array to sort colors */
-         png_ptr->quantize_sort = (png_bytep)png_malloc(png_ptr,
-             (png_uint_32)(num_palette * (sizeof (png_byte))));
+         png_ptr->dither_sort = (png_bytep)png_malloc(png_ptr,
+            (png_uint_32)(num_palette * png_sizeof(png_byte)));
 
-         /* Initialize the quantize_sort array */
+         /* Initialize the dither_sort array */
          for (i = 0; i < num_palette; i++)
-            png_ptr->quantize_sort[i] = (png_byte)i;
+            png_ptr->dither_sort[i] = (png_byte)i;
 
          /* Find the least used palette entries by starting a
           * bubble sort, and running it until we have sorted
           * out enough colors.  Note that we don't care about
           * sorting all the colors, just finding which are
           * least used.
           */
 
          for (i = num_palette - 1; i >= maximum_colors; i--)
          {
             int done; /* To stop early if the list is pre-sorted */
             int j;
 
             done = 1;
             for (j = 0; j < i; j++)
             {
-               if (histogram[png_ptr->quantize_sort[j]]
-                   < histogram[png_ptr->quantize_sort[j + 1]])
+               if (histogram[png_ptr->dither_sort[j]]
+                   < histogram[png_ptr->dither_sort[j + 1]])
                {
                   png_byte t;
 
-                  t = png_ptr->quantize_sort[j];
-                  png_ptr->quantize_sort[j] = png_ptr->quantize_sort[j + 1];
-                  png_ptr->quantize_sort[j + 1] = t;
+                  t = png_ptr->dither_sort[j];
+                  png_ptr->dither_sort[j] = png_ptr->dither_sort[j + 1];
+                  png_ptr->dither_sort[j + 1] = t;
                   done = 0;
                }
             }
-
             if (done)
                break;
          }
 
          /* Swap the palette around, and set up a table, if necessary */
-         if (full_quantize)
+         if (full_dither)
          {
             int j = num_palette;
 
             /* Put all the useful colors within the max, but don't
              * move the others.
              */
             for (i = 0; i < maximum_colors; i++)
             {
-               if ((int)png_ptr->quantize_sort[i] >= maximum_colors)
+               if ((int)png_ptr->dither_sort[i] >= maximum_colors)
                {
                   do
                      j--;
-                  while ((int)png_ptr->quantize_sort[j] >= maximum_colors);
-
+                  while ((int)png_ptr->dither_sort[j] >= maximum_colors);
                   palette[i] = palette[j];
                }
             }
          }
          else
          {
             int j = num_palette;
 
             /* Move all the used colors inside the max limit, and
              * develop a translation table.
              */
             for (i = 0; i < maximum_colors; i++)
             {
                /* Only move the colors we need to */
-               if ((int)png_ptr->quantize_sort[i] >= maximum_colors)
+               if ((int)png_ptr->dither_sort[i] >= maximum_colors)
                {
                   png_color tmp_color;
 
                   do
                      j--;
-                  while ((int)png_ptr->quantize_sort[j] >= maximum_colors);
+                  while ((int)png_ptr->dither_sort[j] >= maximum_colors);
 
                   tmp_color = palette[j];
                   palette[j] = palette[i];
                   palette[i] = tmp_color;
                   /* Indicate where the color went */
-                  png_ptr->quantize_index[j] = (png_byte)i;
-                  png_ptr->quantize_index[i] = (png_byte)j;
+                  png_ptr->dither_index[j] = (png_byte)i;
+                  png_ptr->dither_index[i] = (png_byte)j;
                }
             }
 
             /* Find closest color for those colors we are not using */
             for (i = 0; i < num_palette; i++)
             {
-               if ((int)png_ptr->quantize_index[i] >= maximum_colors)
+               if ((int)png_ptr->dither_index[i] >= maximum_colors)
                {
                   int min_d, k, min_k, d_index;
 
                   /* Find the closest color to one we threw out */
-                  d_index = png_ptr->quantize_index[i];
+                  d_index = png_ptr->dither_index[i];
                   min_d = PNG_COLOR_DIST(palette[d_index], palette[0]);
                   for (k = 1, min_k = 0; k < maximum_colors; k++)
                   {
                      int d;
 
                      d = PNG_COLOR_DIST(palette[d_index], palette[k]);
 
                      if (d < min_d)
                      {
                         min_d = d;
                         min_k = k;
                      }
                   }
                   /* Point to closest color */
-                  png_ptr->quantize_index[i] = (png_byte)min_k;
+                  png_ptr->dither_index[i] = (png_byte)min_k;
                }
             }
          }
-         png_free(png_ptr, png_ptr->quantize_sort);
-         png_ptr->quantize_sort = NULL;
+         png_free(png_ptr, png_ptr->dither_sort);
+         png_ptr->dither_sort = NULL;
       }
       else
       {
          /* This is much harder to do simply (and quickly).  Perhaps
           * we need to go through a median cut routine, but those
           * don't always behave themselves with only a few colors
           * as input.  So we will just find the closest two colors,
           * and throw out one of them (chosen somewhat randomly).
           * [We don't understand this at all, so if someone wants to
           *  work on improving it, be our guest - AED, GRP]
           */
          int i;
          int max_d;
          int num_new_palette;
          png_dsortp t;
          png_dsortpp hash;
 
          t = NULL;
 
          /* Initialize palette index arrays */
          png_ptr->index_to_palette = (png_bytep)png_malloc(png_ptr,
-             (png_uint_32)(num_palette * (sizeof (png_byte))));
+            (png_uint_32)(num_palette * png_sizeof(png_byte)));
          png_ptr->palette_to_index = (png_bytep)png_malloc(png_ptr,
-             (png_uint_32)(num_palette * (sizeof (png_byte))));
+            (png_uint_32)(num_palette * png_sizeof(png_byte)));
 
          /* Initialize the sort array */
          for (i = 0; i < num_palette; i++)
          {
             png_ptr->index_to_palette[i] = (png_byte)i;
             png_ptr->palette_to_index[i] = (png_byte)i;
          }
 
          hash = (png_dsortpp)png_calloc(png_ptr, (png_uint_32)(769 *
-             (sizeof (png_dsortp))));
+            png_sizeof(png_dsortp)));
 
          num_new_palette = num_palette;
 
          /* Initial wild guess at how far apart the farthest pixel
           * pair we will be eliminating will be.  Larger
           * numbers mean more areas will be allocated, Smaller
           * numbers run the risk of not saving enough data, and
           * having to do this all over again.
           *
           * I have not done extensive checking on this number.
           */
          max_d = 96;
 
          while (num_new_palette > maximum_colors)
          {
             for (i = 0; i < num_new_palette - 1; i++)
             {
                int j;
 
                for (j = i + 1; j < num_new_palette; j++)
                {
                   int d;
 
                   d = PNG_COLOR_DIST(palette[i], palette[j]);
 
                   if (d <= max_d)
                   {
 
                      t = (png_dsortp)png_malloc_warn(png_ptr,
-                         (png_uint_32)(sizeof (png_dsort)));
-
+                         (png_uint_32)(png_sizeof(png_dsort)));
                      if (t == NULL)
                          break;
-
                      t->next = hash[d];
                      t->left = (png_byte)i;
                      t->right = (png_byte)j;
                      hash[d] = t;
                   }
                }
                if (t == NULL)
                   break;
             }
 
             if (t != NULL)
             for (i = 0; i <= max_d; i++)
             {
                if (hash[i] != NULL)
                {
                   png_dsortp p;
 
                   for (p = hash[i]; p; p = p->next)
                   {
                      if ((int)png_ptr->index_to_palette[p->left]
-                         < num_new_palette &&
-                         (int)png_ptr->index_to_palette[p->right]
-                         < num_new_palette)
+                        < num_new_palette &&
+                        (int)png_ptr->index_to_palette[p->right]
+                        < num_new_palette)
                      {
                         int j, next_j;
 
                         if (num_new_palette & 0x01)
                         {
                            j = p->left;
                            next_j = p->right;
                         }
                         else
                         {
                            j = p->right;
                            next_j = p->left;
                         }
 
                         num_new_palette--;
                         palette[png_ptr->index_to_palette[j]]
-                            = palette[num_new_palette];
-                        if (!full_quantize)
+                          = palette[num_new_palette];
+                        if (!full_dither)
                         {
                            int k;
 
                            for (k = 0; k < num_palette; k++)
                            {
-                              if (png_ptr->quantize_index[k] ==
-                                  png_ptr->index_to_palette[j])
-                                 png_ptr->quantize_index[k] =
-                                     png_ptr->index_to_palette[next_j];
-
-                              if ((int)png_ptr->quantize_index[k] ==
-                                  num_new_palette)
-                                 png_ptr->quantize_index[k] =
-                                     png_ptr->index_to_palette[j];
+                              if (png_ptr->dither_index[k] ==
+                                 png_ptr->index_to_palette[j])
+                                 png_ptr->dither_index[k] =
+                                    png_ptr->index_to_palette[next_j];
+                              if ((int)png_ptr->dither_index[k] ==
+                                 num_new_palette)
+                                 png_ptr->dither_index[k] =
+                                    png_ptr->index_to_palette[j];
                            }
                         }
 
                         png_ptr->index_to_palette[png_ptr->palette_to_index
-                            [num_new_palette]] = png_ptr->index_to_palette[j];
-
+                           [num_new_palette]] = png_ptr->index_to_palette[j];
                         png_ptr->palette_to_index[png_ptr->index_to_palette[j]]
-                            = png_ptr->palette_to_index[num_new_palette];
+                           = png_ptr->palette_to_index[num_new_palette];
 
                         png_ptr->index_to_palette[j] =
                             (png_byte)num_new_palette;
-
                         png_ptr->palette_to_index[num_new_palette] =
                             (png_byte)j;
                      }
                      if (num_new_palette <= maximum_colors)
                         break;
                   }
                   if (num_new_palette <= maximum_colors)
                      break;
                }
             }
@@ skipping 21 matching lines @@
          png_ptr->index_to_palette = NULL;
       }
       num_palette = maximum_colors;
    }
    if (png_ptr->palette == NULL)
    {
       png_ptr->palette = palette;
    }
    png_ptr->num_palette = (png_uint_16)num_palette;
 
-   if (full_quantize)
+   if (full_dither)
    {
       int i;
       png_bytep distance;
-      int total_bits = PNG_QUANTIZE_RED_BITS + PNG_QUANTIZE_GREEN_BITS +
-          PNG_QUANTIZE_BLUE_BITS;
-      int num_red = (1 << PNG_QUANTIZE_RED_BITS);
-      int num_green = (1 << PNG_QUANTIZE_GREEN_BITS);
-      int num_blue = (1 << PNG_QUANTIZE_BLUE_BITS);
+      int total_bits = PNG_DITHER_RED_BITS + PNG_DITHER_GREEN_BITS +
+         PNG_DITHER_BLUE_BITS;
+      int num_red = (1 << PNG_DITHER_RED_BITS);
+      int num_green = (1 << PNG_DITHER_GREEN_BITS);
+      int num_blue = (1 << PNG_DITHER_BLUE_BITS);
       png_size_t num_entries = ((png_size_t)1 << total_bits);
 
-      png_ptr->palette_lookup = (png_bytep)png_calloc(png_ptr,
-          (png_uint_32)(num_entries * (sizeof (png_byte))));
+      png_ptr->palette_lookup = (png_bytep )png_calloc(png_ptr,
+         (png_uint_32)(num_entries * png_sizeof(png_byte)));
 
       distance = (png_bytep)png_malloc(png_ptr, (png_uint_32)(num_entries *
-          (sizeof (png_byte))));
-
-      memset(distance, 0xff, num_entries * (sizeof (png_byte)));
+         png_sizeof(png_byte)));
+      png_memset(distance, 0xff, num_entries * png_sizeof(png_byte));
 
       for (i = 0; i < num_palette; i++)
       {
          int ir, ig, ib;
-         int r = (palette[i].red >> (8 - PNG_QUANTIZE_RED_BITS));
-         int g = (palette[i].green >> (8 - PNG_QUANTIZE_GREEN_BITS));
-         int b = (palette[i].blue >> (8 - PNG_QUANTIZE_BLUE_BITS));
+         int r = (palette[i].red >> (8 - PNG_DITHER_RED_BITS));
+         int g = (palette[i].green >> (8 - PNG_DITHER_GREEN_BITS));
+         int b = (palette[i].blue >> (8 - PNG_DITHER_BLUE_BITS));
 
          for (ir = 0; ir < num_red; ir++)
          {
             /* int dr = abs(ir - r); */
             int dr = ((ir > r) ? ir - r : r - ir);
-            int index_r = (ir << (PNG_QUANTIZE_BLUE_BITS +
-                PNG_QUANTIZE_GREEN_BITS));
+            int index_r = (ir << (PNG_DITHER_BLUE_BITS +
+                PNG_DITHER_GREEN_BITS));
 
             for (ig = 0; ig < num_green; ig++)
             {
                /* int dg = abs(ig - g); */
                int dg = ((ig > g) ? ig - g : g - ig);
                int dt = dr + dg;
                int dm = ((dr > dg) ? dr : dg);
-               int index_g = index_r | (ig << PNG_QUANTIZE_BLUE_BITS);
+               int index_g = index_r | (ig << PNG_DITHER_BLUE_BITS);
 
                for (ib = 0; ib < num_blue; ib++)
                {
                   int d_index = index_g | ib;
                   /* int db = abs(ib - b); */
                   int db = ((ib > b) ? ib - b : b - ib);
                   int dmax = ((dm > db) ? dm : db);
                   int d = dmax + dt + db;
 
                   if (d < (int)distance[d_index])
                   {
                      distance[d_index] = (png_byte)d;
                      png_ptr->palette_lookup[d_index] = (png_byte)i;
                   }
                }
             }
          }
       }
 
       png_free(png_ptr, distance);
    }
 }
-#endif /* PNG_READ_QUANTIZE_SUPPORTED */
+#endif
 
-#ifdef PNG_READ_GAMMA_SUPPORTED
-void PNGFAPI
-png_set_gamma_fixed(png_structrp png_ptr, png_fixed_point scrn_gamma,
-   png_fixed_point file_gamma)
+#if defined(PNG_READ_GAMMA_SUPPORTED) && defined(PNG_FLOATING_POINT_SUPPORTED)
+/* Transform the image from the file_gamma to the screen_gamma.  We
+ * only do transformations on images where the file_gamma and screen_gamma
+ * are not close reciprocals, otherwise it slows things down slightly, and
+ * also needlessly introduces small errors.
+ *
+ * We will turn off gamma transformation later if no semitransparent entries
+ * are present in the tRNS array for palette images.  We can't do it here
+ * because we don't necessarily have the tRNS chunk yet.
+ */
+void PNGAPI
+png_set_gamma(png_structp png_ptr, double scrn_gamma, double file_gamma)
 {
-   png_debug(1, "in png_set_gamma_fixed");
+   png_debug(1, "in png_set_gamma");
 
-   if (!png_rtran_ok(png_ptr, 0))
+   if (png_ptr == NULL)
       return;
 
-   /* New in libpng-1.5.4 - reserve particular negative values as flags. */
-   scrn_gamma = translate_gamma_flags(png_ptr, scrn_gamma, 1/*screen*/);
-   file_gamma = translate_gamma_flags(png_ptr, file_gamma, 0/*file*/);
-
-   /* Checking the gamma values for being >0 was added in 1.5.4 along with the
-    * premultiplied alpha support; this actually hides an undocumented feature
-    * of the previous implementation which allowed gamma processing to be
-    * disabled in background handling.  There is no evidence (so far) that this
-    * was being used; however, png_set_background itself accepted and must still
-    * accept '0' for the gamma value it takes, because it isn't always used.
-    *
-    * Since this is an API change (albeit a very minor one that removes an
-    * undocumented API feature) the following checks were only enabled in
-    * libpng-1.6.0.
-    */
-   if (file_gamma <= 0)
-      png_error(png_ptr, "invalid file gamma in png_set_gamma");
-
-   if (scrn_gamma <= 0)
-      png_error(png_ptr, "invalid screen gamma in png_set_gamma");
-
-   /* Set the gamma values unconditionally - this overrides the value in the PNG
-    * file if a gAMA chunk was present.  png_set_alpha_mode provides a
-    * different, easier, way to default the file gamma.
-    */
-   png_ptr->colorspace.gamma = file_gamma;
-   png_ptr->colorspace.flags |= PNG_COLORSPACE_HAVE_GAMMA;
-   png_ptr->screen_gamma = scrn_gamma;
+   if ((fabs(scrn_gamma * file_gamma - 1.0) > PNG_GAMMA_THRESHOLD) ||
+       (png_ptr->color_type & PNG_COLOR_MASK_ALPHA) ||
+       (png_ptr->color_type == PNG_COLOR_TYPE_PALETTE))
+     png_ptr->transformations |= PNG_GAMMA;
+   png_ptr->gamma = (float)file_gamma;
+   png_ptr->screen_gamma = (float)scrn_gamma;
 }
-
-#  ifdef PNG_FLOATING_POINT_SUPPORTED
-void PNGAPI
-png_set_gamma(png_structrp png_ptr, double scrn_gamma, double file_gamma)
-{
-   png_set_gamma_fixed(png_ptr, convert_gamma_value(png_ptr, scrn_gamma),
-      convert_gamma_value(png_ptr, file_gamma));
-}
-#  endif /* FLOATING_POINT_SUPPORTED */
-#endif /* READ_GAMMA */
+#endif
 
 #ifdef PNG_READ_EXPAND_SUPPORTED
 /* Expand paletted images to RGB, expand grayscale images of
  * less than 8-bit depth to 8-bit depth, and expand tRNS chunks
  * to alpha channels.
  */
 void PNGAPI
-png_set_expand(png_structrp png_ptr)
+png_set_expand(png_structp png_ptr)
 {
    png_debug(1, "in png_set_expand");
 
-   if (!png_rtran_ok(png_ptr, 0))
+   if (png_ptr == NULL)
       return;
 
    png_ptr->transformations |= (PNG_EXPAND | PNG_EXPAND_tRNS);
+   png_ptr->flags &= ~PNG_FLAG_ROW_INIT;
 }
 
 /* GRR 19990627:  the following three functions currently are identical
  *  to png_set_expand().  However, it is entirely reasonable that someone
  *  might wish to expand an indexed image to RGB but *not* expand a single,
  *  fully transparent palette entry to a full alpha channel--perhaps instead
  *  convert tRNS to the grayscale/RGB format (16-bit RGB value), or replace
  *  the transparent color with a particular RGB value, or drop tRNS entirely.
  *  IOW, a future version of the library may make the transformations flag
  *  a bit more fine-grained, with separate bits for each of these three
  *  functions.
  *
  *  More to the point, these functions make it obvious what libpng will be
  *  doing, whereas "expand" can (and does) mean any number of things.
  *
  *  GRP 20060307: In libpng-1.2.9, png_set_gray_1_2_4_to_8() was modified
  *  to expand only the sample depth but not to expand the tRNS to alpha
  *  and its name was changed to png_set_expand_gray_1_2_4_to_8().
  */
 
 /* Expand paletted images to RGB. */
 void PNGAPI
-png_set_palette_to_rgb(png_structrp png_ptr)
+png_set_palette_to_rgb(png_structp png_ptr)
 {
    png_debug(1, "in png_set_palette_to_rgb");
 
-   if (!png_rtran_ok(png_ptr, 0))
+   if (png_ptr == NULL)
       return;
 
    png_ptr->transformations |= (PNG_EXPAND | PNG_EXPAND_tRNS);
-}
-
+   png_ptr->flags &= ~PNG_FLAG_ROW_INIT;
+}
+
+#ifndef PNG_1_0_X
 /* Expand grayscale images of less than 8-bit depth to 8 bits. */
 void PNGAPI
-png_set_expand_gray_1_2_4_to_8(png_structrp png_ptr)
+png_set_expand_gray_1_2_4_to_8(png_structp png_ptr)
 {
    png_debug(1, "in png_set_expand_gray_1_2_4_to_8");
 
-   if (!png_rtran_ok(png_ptr, 0))
+   if (png_ptr == NULL)
       return;
 
    png_ptr->transformations |= PNG_EXPAND;
-}
+   png_ptr->flags &= ~PNG_FLAG_ROW_INIT;
+}
+#endif
+
+#if defined(PNG_1_0_X) || defined(PNG_1_2_X)
+/* Expand grayscale images of less than 8-bit depth to 8 bits. */
+/* Deprecated as of libpng-1.2.9 */
+void PNGAPI
+png_set_gray_1_2_4_to_8(png_structp png_ptr)
+{
+   png_debug(1, "in png_set_gray_1_2_4_to_8");
+
+   if (png_ptr == NULL)
+      return;
+
+   png_ptr->transformations |= (PNG_EXPAND | PNG_EXPAND_tRNS);
+}
+#endif
+
 
 /* Expand tRNS chunks to alpha channels. */
 void PNGAPI
-png_set_tRNS_to_alpha(png_structrp png_ptr)
+png_set_tRNS_to_alpha(png_structp png_ptr)
 {
    png_debug(1, "in png_set_tRNS_to_alpha");
 
-   if (!png_rtran_ok(png_ptr, 0))
-      return;
-
    png_ptr->transformations |= (PNG_EXPAND | PNG_EXPAND_tRNS);
+   png_ptr->flags &= ~PNG_FLAG_ROW_INIT;
 }
 #endif /* defined(PNG_READ_EXPAND_SUPPORTED) */
 
-#ifdef PNG_READ_EXPAND_16_SUPPORTED
-/* Expand to 16-bit channels, expand the tRNS chunk too (because otherwise
- * it may not work correctly.)
+#ifdef PNG_READ_GRAY_TO_RGB_SUPPORTED
+void PNGAPI
+png_set_gray_to_rgb(png_structp png_ptr)
+{
+   png_debug(1, "in png_set_gray_to_rgb");
+
+   png_ptr->transformations |= PNG_GRAY_TO_RGB;
+   png_ptr->flags &= ~PNG_FLAG_ROW_INIT;
+}
+#endif
+
+#ifdef PNG_READ_RGB_TO_GRAY_SUPPORTED
+#ifdef PNG_FLOATING_POINT_SUPPORTED
+/* Convert a RGB image to a grayscale of the same width.  This allows us,
+ * for example, to convert a 24 bpp RGB image into an 8 bpp grayscale image.
  */
-void PNGAPI
-png_set_expand_16(png_structrp png_ptr)
-{
-   png_debug(1, "in png_set_expand_16");
-
-   if (!png_rtran_ok(png_ptr, 0))
-      return;
-
-   png_ptr->transformations |= (PNG_EXPAND_16 | PNG_EXPAND | PNG_EXPAND_tRNS);
-}
-#endif
-
-#ifdef PNG_READ_GRAY_TO_RGB_SUPPORTED
-void PNGAPI
-png_set_gray_to_rgb(png_structrp png_ptr)
-{
-   png_debug(1, "in png_set_gray_to_rgb");
-
-   if (!png_rtran_ok(png_ptr, 0))
-      return;
-
-   /* Because rgb must be 8 bits or more: */
-   png_set_expand_gray_1_2_4_to_8(png_ptr);
-   png_ptr->transformations |= PNG_GRAY_TO_RGB;
-}
-#endif
-
-#ifdef PNG_READ_RGB_TO_GRAY_SUPPORTED
-void PNGFAPI
-png_set_rgb_to_gray_fixed(png_structrp png_ptr, int error_action,
-    png_fixed_point red, png_fixed_point green)
+
+void PNGAPI
+png_set_rgb_to_gray(png_structp png_ptr, int error_action, double red,
+   double green)
+{
+   int red_fixed, green_fixed;
+   if (png_ptr == NULL)
+      return;
+   if (red > 21474.83647 || red < -21474.83648 ||
+       green > 21474.83647 || green < -21474.83648)
+   {
+      png_warning(png_ptr, "ignoring out of range rgb_to_gray coefficients");
+      red_fixed = -1;
+      green_fixed = -1;
+   }
+   else
+   {
+      red_fixed = (int)((float)red*100000.0 + 0.5);
+      green_fixed = (int)((float)green*100000.0 + 0.5);
+   }
+   png_set_rgb_to_gray_fixed(png_ptr, error_action, red_fixed, green_fixed);
+}
+#endif
+
+void PNGAPI
+png_set_rgb_to_gray_fixed(png_structp png_ptr, int error_action,
+   png_fixed_point red, png_fixed_point green)
 {
    png_debug(1, "in png_set_rgb_to_gray");
 
-   /* Need the IHDR here because of the check on color_type below. */
-   /* TODO: fix this */
-   if (!png_rtran_ok(png_ptr, 1))
+   if (png_ptr == NULL)
       return;
 
    switch(error_action)
    {
-      case PNG_ERROR_ACTION_NONE:
-         png_ptr->transformations |= PNG_RGB_TO_GRAY;
-         break;
-
-      case PNG_ERROR_ACTION_WARN:
-         png_ptr->transformations |= PNG_RGB_TO_GRAY_WARN;
-         break;
-
-      case PNG_ERROR_ACTION_ERROR:
-         png_ptr->transformations |= PNG_RGB_TO_GRAY_ERR;
-         break;
-
-      default:
-         png_error(png_ptr, "invalid error action to rgb_to_gray");
-         break;
-   }
-
+      case 1: png_ptr->transformations |= PNG_RGB_TO_GRAY;
+              break;
+
+      case 2: png_ptr->transformations |= PNG_RGB_TO_GRAY_WARN;
+              break;
+
+      case 3: png_ptr->transformations |= PNG_RGB_TO_GRAY_ERR;
+   }
    if (png_ptr->color_type == PNG_COLOR_TYPE_PALETTE)
 #ifdef PNG_READ_EXPAND_SUPPORTED
       png_ptr->transformations |= PNG_EXPAND;
 #else
    {
-      /* Make this an error in 1.6 because otherwise the application may assume
-       * that it just worked and get a memory overwrite.
-       */
-      png_error(png_ptr,
-        "Cannot do RGB_TO_GRAY without EXPAND_SUPPORTED");
-
-      /* png_ptr->transformations &= ~PNG_RGB_TO_GRAY; */
-   }
-#endif
-   {
-      if (red >= 0 && green >= 0 && red + green <= PNG_FP_1)
-      {
-         png_uint_16 red_int, green_int;
-
-         /* NOTE: this calculation does not round, but this behavior is retained
-          * for consistency, the inaccuracy is very small.  The code here always
-          * overwrites the coefficients, regardless of whether they have been
-          * defaulted or set already.
-          */
-         red_int = (png_uint_16)(((png_uint_32)red*32768)/100000);
-         green_int = (png_uint_16)(((png_uint_32)green*32768)/100000);
-
-         png_ptr->rgb_to_gray_red_coeff   = red_int;
-         png_ptr->rgb_to_gray_green_coeff = green_int;
-         png_ptr->rgb_to_gray_coefficients_set = 1;
-      }
-
+      png_warning(png_ptr,
+        "Cannot do RGB_TO_GRAY without EXPAND_SUPPORTED.");
+      png_ptr->transformations &= ~PNG_RGB_TO_GRAY;
+   }
+#endif
+   {
+      png_uint_16 red_int, green_int;
+      if (red < 0 || green < 0)
+      {
+         red_int   =  6968; /* .212671 * 32768 + .5 */
+         green_int = 23434; /* .715160 * 32768 + .5 */
+      }
+      else if (red + green < 100000L)
+      {
+         red_int = (png_uint_16)(((png_uint_32)red*32768L)/100000L);
+         green_int = (png_uint_16)(((png_uint_32)green*32768L)/100000L);
+      }
       else
       {
-         if (red >= 0 && green >= 0)
-            png_app_warning(png_ptr,
-               "ignoring out of range rgb_to_gray coefficients");
-
-         /* Use the defaults, from the cHRM chunk if set, else the historical
-          * values which are close to the sRGB/HDTV/ITU-Rec 709 values.  See
-          * png_do_rgb_to_gray for more discussion of the values.  In this case
-          * the coefficients are not marked as 'set' and are not overwritten if
-          * something has already provided a default.
-          */
-         if (png_ptr->rgb_to_gray_red_coeff == 0 &&
-            png_ptr->rgb_to_gray_green_coeff == 0)
-         {
-            png_ptr->rgb_to_gray_red_coeff   = 6968;
-            png_ptr->rgb_to_gray_green_coeff = 23434;
-            /* png_ptr->rgb_to_gray_blue_coeff  = 2366; */
-         }
-      }
-   }
-}
-
-#ifdef PNG_FLOATING_POINT_SUPPORTED
-/* Convert a RGB image to a grayscale of the same width.  This allows us,
- * for example, to convert a 24 bpp RGB image into an 8 bpp grayscale image.
- */
-
-void PNGAPI
-png_set_rgb_to_gray(png_structrp png_ptr, int error_action, double red,
-   double green)
-{
-   png_set_rgb_to_gray_fixed(png_ptr, error_action,
-      png_fixed(png_ptr, red, "rgb to gray red coefficient"),
-      png_fixed(png_ptr, green, "rgb to gray green coefficient"));
-}
-#endif /* FLOATING POINT */
-
-#endif /* RGB_TO_GRAY */
+         png_warning(png_ptr, "ignoring out of range rgb_to_gray coefficients");
+         red_int   =  6968;
+         green_int = 23434;
+      }
+      png_ptr->rgb_to_gray_red_coeff   = red_int;
+      png_ptr->rgb_to_gray_green_coeff = green_int;
+      png_ptr->rgb_to_gray_blue_coeff  =
+         (png_uint_16)(32768 - red_int - green_int);
+   }
+}
+#endif
 
 #if defined(PNG_READ_USER_TRANSFORM_SUPPORTED) || \
+    defined(PNG_LEGACY_SUPPORTED) || \
     defined(PNG_WRITE_USER_TRANSFORM_SUPPORTED)
 void PNGAPI
-png_set_read_user_transform_fn(png_structrp png_ptr, png_user_transform_ptr
-    read_user_transform_fn)
+png_set_read_user_transform_fn(png_structp png_ptr, png_user_transform_ptr
+   read_user_transform_fn)
 {
    png_debug(1, "in png_set_read_user_transform_fn");
 
+   if (png_ptr == NULL)
+      return;
+
 #ifdef PNG_READ_USER_TRANSFORM_SUPPORTED
    png_ptr->transformations |= PNG_USER_TRANSFORM;
    png_ptr->read_user_transform_fn = read_user_transform_fn;
 #endif
-}
-#endif
-
-#ifdef PNG_READ_TRANSFORMS_SUPPORTED
-#ifdef PNG_READ_GAMMA_SUPPORTED
-/* In the case of gamma transformations only do transformations on images where
- * the [file] gamma and screen_gamma are not close reciprocals, otherwise it
- * slows things down slightly, and also needlessly introduces small errors.
- */
-static int /* PRIVATE */
-png_gamma_threshold(png_fixed_point screen_gamma, png_fixed_point file_gamma)
-{
-   /* PNG_GAMMA_THRESHOLD is the threshold for performing gamma
-    * correction as a difference of the overall transform from 1.0
-    *
-    * We want to compare the threshold with s*f - 1, if we get
-    * overflow here it is because of wacky gamma values so we
-    * turn on processing anyway.
-    */
-   png_fixed_point gtest;
-   return !png_muldiv(&gtest, screen_gamma, file_gamma, PNG_FP_1) ||
-       png_gamma_significant(gtest);
+#ifdef PNG_LEGACY_SUPPORTED
+   if (read_user_transform_fn)
+      png_warning(png_ptr,
+        "This version of libpng does not support user transforms");
+#endif
 }
 #endif
 
 /* Initialize everything needed for the read.  This includes modifying
  * the palette.
  */
-
-/*For the moment 'png_init_palette_transformations' and
- * 'png_init_rgb_transformations' only do some flag canceling optimizations.
- * The intent is that these two routines should have palette or rgb operations
- * extracted from 'png_init_read_transformations'.
- */
-static void /* PRIVATE */
-png_init_palette_transformations(png_structrp png_ptr)
-{
-   /* Called to handle the (input) palette case.  In png_do_read_transformations
-    * the first step is to expand the palette if requested, so this code must
-    * take care to only make changes that are invariant with respect to the
-    * palette expansion, or only do them if there is no expansion.
-    *
-    * STRIP_ALPHA has already been handled in the caller (by setting num_trans
-    * to 0.)
-    */
-   int input_has_alpha = 0;
-   int input_has_transparency = 0;
-
-   if (png_ptr->num_trans > 0)
-   {
-      int i;
-
-      /* Ignore if all the entries are opaque (unlikely!) */
-      for (i=0; i<png_ptr->num_trans; ++i)
-         if (png_ptr->trans_alpha[i] == 255)
-            continue;
-         else if (png_ptr->trans_alpha[i] == 0)
-            input_has_transparency = 1;
-         else
-            input_has_alpha = 1;
-   }
-
-   /* If no alpha we can optimize. */
-   if (!input_has_alpha)
-   {
-      /* Any alpha means background and associative alpha processing is
-       * required, however if the alpha is 0 or 1 throughout OPTIIMIZE_ALPHA
-       * and ENCODE_ALPHA are irrelevant.
-       */
-      png_ptr->transformations &= ~PNG_ENCODE_ALPHA;
-      png_ptr->flags &= ~PNG_FLAG_OPTIMIZE_ALPHA;
-
-      if (!input_has_transparency)
-         png_ptr->transformations &= ~(PNG_COMPOSE | PNG_BACKGROUND_EXPAND);
-   }
+void /* PRIVATE */
+png_init_read_transformations(png_structp png_ptr)
+{
+   png_debug(1, "in png_init_read_transformations");
+
+#ifdef PNG_USELESS_TESTS_SUPPORTED
+  if (png_ptr != NULL)
+#endif
+  {
+#if defined(PNG_READ_BACKGROUND_SUPPORTED) || \
+    defined(PNG_READ_SHIFT_SUPPORTED) || \
+    defined(PNG_READ_GAMMA_SUPPORTED)
+   int color_type = png_ptr->color_type;
+#endif
 
 #if defined(PNG_READ_EXPAND_SUPPORTED) && defined(PNG_READ_BACKGROUND_SUPPORTED)
-   /* png_set_background handling - deals with the complexity of whether the
-    * background color is in the file format or the screen format in the case
-    * where an 'expand' will happen.
-    */
-
-   /* The following code cannot be entered in the alpha pre-multiplication case
-    * because PNG_BACKGROUND_EXPAND is cancelled below.
-    */
-   if ((png_ptr->transformations & PNG_BACKGROUND_EXPAND) &&
-       (png_ptr->transformations & PNG_EXPAND))
-   {
-      {
-         png_ptr->background.red   =
-             png_ptr->palette[png_ptr->background.index].red;
-         png_ptr->background.green =
-             png_ptr->palette[png_ptr->background.index].green;
-         png_ptr->background.blue  =
-             png_ptr->palette[png_ptr->background.index].blue;
-
-#ifdef PNG_READ_INVERT_ALPHA_SUPPORTED
-        if (png_ptr->transformations & PNG_INVERT_ALPHA)
-        {
-           if (!(png_ptr->transformations & PNG_EXPAND_tRNS))
-           {
-              /* Invert the alpha channel (in tRNS) unless the pixels are
-               * going to be expanded, in which case leave it for later
-               */
-              int i, istop = png_ptr->num_trans;
-
-              for (i=0; i<istop; i++)
-                 png_ptr->trans_alpha[i] = (png_byte)(255 -
-                    png_ptr->trans_alpha[i]);
-           }
-        }
-#endif /* PNG_READ_INVERT_ALPHA_SUPPORTED */
-      }
-   } /* background expand and (therefore) no alpha association. */
-#endif /* PNG_READ_EXPAND_SUPPORTED && PNG_READ_BACKGROUND_SUPPORTED */
-}
-
-static void /* PRIVATE */
-png_init_rgb_transformations(png_structrp png_ptr)
-{
-   /* Added to libpng-1.5.4: check the color type to determine whether there
-    * is any alpha or transparency in the image and simply cancel the
-    * background and alpha mode stuff if there isn't.
-    */
-   int input_has_alpha = (png_ptr->color_type & PNG_COLOR_MASK_ALPHA) != 0;
-   int input_has_transparency = png_ptr->num_trans > 0;
-
-   /* If no alpha we can optimize. */
-   if (!input_has_alpha)
-   {
-      /* Any alpha means background and associative alpha processing is
-       * required, however if the alpha is 0 or 1 throughout OPTIIMIZE_ALPHA
-       * and ENCODE_ALPHA are irrelevant.
-       */
-#     ifdef PNG_READ_ALPHA_MODE_SUPPORTED
-         png_ptr->transformations &= ~PNG_ENCODE_ALPHA;
-         png_ptr->flags &= ~PNG_FLAG_OPTIMIZE_ALPHA;
-#     endif
-
-      if (!input_has_transparency)
-         png_ptr->transformations &= ~(PNG_COMPOSE | PNG_BACKGROUND_EXPAND);
-   }
-
-#if defined(PNG_READ_EXPAND_SUPPORTED) && defined(PNG_READ_BACKGROUND_SUPPORTED)
-   /* png_set_background handling - deals with the complexity of whether the
-    * background color is in the file format or the screen format in the case
-    * where an 'expand' will happen.
-    */
-
-   /* The following code cannot be entered in the alpha pre-multiplication case
-    * because PNG_BACKGROUND_EXPAND is cancelled below.
-    */
-   if ((png_ptr->transformations & PNG_BACKGROUND_EXPAND) &&
-       (png_ptr->transformations & PNG_EXPAND) &&
-       !(png_ptr->color_type & PNG_COLOR_MASK_COLOR))
-       /* i.e., GRAY or GRAY_ALPHA */
-   {
-      {
-         /* Expand background and tRNS chunks */
-         int gray = png_ptr->background.gray;
-         int trans_gray = png_ptr->trans_color.gray;
-
-         switch (png_ptr->bit_depth)
-         {
-            case 1:
-               gray *= 0xff;
-               trans_gray *= 0xff;
-               break;
-
-            case 2:
-               gray *= 0x55;
-               trans_gray *= 0x55;
-               break;
-
-            case 4:
-               gray *= 0x11;
-               trans_gray *= 0x11;
-               break;
-
-            default:
-
-            case 8:
-               /* FALL THROUGH (Already 8 bits) */
-
-            case 16:
-               /* Already a full 16 bits */
-               break;
-         }
-
-         png_ptr->background.red = png_ptr->background.green =
-            png_ptr->background.blue = (png_uint_16)gray;
-
-         if (!(png_ptr->transformations & PNG_EXPAND_tRNS))
-         {
-            png_ptr->trans_color.red = png_ptr->trans_color.green =
-               png_ptr->trans_color.blue = (png_uint_16)trans_gray;
-         }
-      }
-   } /* background expand and (therefore) no alpha association. */
-#endif /* PNG_READ_EXPAND_SUPPORTED && PNG_READ_BACKGROUND_SUPPORTED */
-}
-
-void /* PRIVATE */
-png_init_read_transformations(png_structrp png_ptr)
-{
-   png_debug(1, "in png_init_read_transformations");
-
-   /* This internal function is called from png_read_start_row in pngrutil.c
-    * and it is called before the 'rowbytes' calculation is done, so the code
-    * in here can change or update the transformations flags.
-    *
-    * First do updates that do not depend on the details of the PNG image data
-    * being processed.
-    */
-
-#ifdef PNG_READ_GAMMA_SUPPORTED
-   /* Prior to 1.5.4 these tests were performed from png_set_gamma, 1.5.4 adds
-    * png_set_alpha_mode and this is another source for a default file gamma so
-    * the test needs to be performed later - here.  In addition prior to 1.5.4
-    * the tests were repeated for the PALETTE color type here - this is no
-    * longer necessary (and doesn't seem to have been necessary before.)
-    */
-   {
-      /* The following temporary indicates if overall gamma correction is
-       * required.
-       */
-      int gamma_correction = 0;
-
-      if (png_ptr->colorspace.gamma != 0) /* has been set */
-      {
-         if (png_ptr->screen_gamma != 0) /* screen set too */
-            gamma_correction = png_gamma_threshold(png_ptr->colorspace.gamma,
-               png_ptr->screen_gamma);
-
-         else
-            /* Assume the output matches the input; a long time default behavior
-             * of libpng, although the standard has nothing to say about this.
-             */
-            png_ptr->screen_gamma = png_reciprocal(png_ptr->colorspace.gamma);
-      }
-
-      else if (png_ptr->screen_gamma != 0)
-         /* The converse - assume the file matches the screen, note that this
-          * perhaps undesireable default can (from 1.5.4) be changed by calling
-          * png_set_alpha_mode (even if the alpha handling mode isn't required
-          * or isn't changed from the default.)
-          */
-         png_ptr->colorspace.gamma = png_reciprocal(png_ptr->screen_gamma);
-
-      else /* neither are set */
-         /* Just in case the following prevents any processing - file and screen
-          * are both assumed to be linear and there is no way to introduce a
-          * third gamma value other than png_set_background with 'UNIQUE', and,
-          * prior to 1.5.4
-          */
-         png_ptr->screen_gamma = png_ptr->colorspace.gamma = PNG_FP_1;
-
-      /* We have a gamma value now. */
-      png_ptr->colorspace.flags |= PNG_COLORSPACE_HAVE_GAMMA;
-
-      /* Now turn the gamma transformation on or off as appropriate.  Notice
-       * that PNG_GAMMA just refers to the file->screen correction.  Alpha
-       * composition may independently cause gamma correction because it needs
-       * linear data (e.g. if the file has a gAMA chunk but the screen gamma
-       * hasn't been specified.)  In any case this flag may get turned off in
-       * the code immediately below if the transform can be handled outside the
-       * row loop.
-       */
-      if (gamma_correction)
-         png_ptr->transformations |= PNG_GAMMA;
-
-      else
-         png_ptr->transformations &= ~PNG_GAMMA;
-   }
-#endif
-
-   /* Certain transformations have the effect of preventing other
-    * transformations that happen afterward in png_do_read_transformations,
-    * resolve the interdependencies here.  From the code of
-    * png_do_read_transformations the order is:
-    *
-    *  1) PNG_EXPAND (including PNG_EXPAND_tRNS)
-    *  2) PNG_STRIP_ALPHA (if no compose)
-    *  3) PNG_RGB_TO_GRAY
-    *  4) PNG_GRAY_TO_RGB iff !PNG_BACKGROUND_IS_GRAY
-    *  5) PNG_COMPOSE
-    *  6) PNG_GAMMA
-    *  7) PNG_STRIP_ALPHA (if compose)
-    *  8) PNG_ENCODE_ALPHA
-    *  9) PNG_SCALE_16_TO_8
-    * 10) PNG_16_TO_8
-    * 11) PNG_QUANTIZE (converts to palette)
-    * 12) PNG_EXPAND_16
-    * 13) PNG_GRAY_TO_RGB iff PNG_BACKGROUND_IS_GRAY
-    * 14) PNG_INVERT_MONO
-    * 15) PNG_SHIFT
-    * 16) PNG_PACK
-    * 17) PNG_BGR
-    * 18) PNG_PACKSWAP
-    * 19) PNG_FILLER (includes PNG_ADD_ALPHA)
-    * 20) PNG_INVERT_ALPHA
-    * 21) PNG_SWAP_ALPHA
-    * 22) PNG_SWAP_BYTES
-    * 23) PNG_USER_TRANSFORM [must be last]
-    */
-#ifdef PNG_READ_STRIP_ALPHA_SUPPORTED
-   if ((png_ptr->transformations & PNG_STRIP_ALPHA) &&
-      !(png_ptr->transformations & PNG_COMPOSE))
-   {
-      /* Stripping the alpha channel happens immediately after the 'expand'
-       * transformations, before all other transformation, so it cancels out
-       * the alpha handling.  It has the side effect negating the effect of
-       * PNG_EXPAND_tRNS too:
-       */
-      png_ptr->transformations &= ~(PNG_BACKGROUND_EXPAND | PNG_ENCODE_ALPHA |
-         PNG_EXPAND_tRNS);
-      png_ptr->flags &= ~PNG_FLAG_OPTIMIZE_ALPHA;
-
-      /* Kill the tRNS chunk itself too.  Prior to 1.5.4 this did not happen
-       * so transparency information would remain just so long as it wasn't
-       * expanded.  This produces unexpected API changes if the set of things
-       * that do PNG_EXPAND_tRNS changes (perfectly possible given the
-       * documentation - which says ask for what you want, accept what you
-       * get.)  This makes the behavior consistent from 1.5.4:
-       */
-      png_ptr->num_trans = 0;
-   }
-#endif /* STRIP_ALPHA supported, no COMPOSE */
-
-#ifdef PNG_READ_ALPHA_MODE_SUPPORTED
-   /* If the screen gamma is about 1.0 then the OPTIMIZE_ALPHA and ENCODE_ALPHA
-    * settings will have no effect.
-    */
-   if (!png_gamma_significant(png_ptr->screen_gamma))
-   {
-      png_ptr->transformations &= ~PNG_ENCODE_ALPHA;
-      png_ptr->flags &= ~PNG_FLAG_OPTIMIZE_ALPHA;
-   }
-#endif
-
-#ifdef PNG_READ_RGB_TO_GRAY_SUPPORTED
-   /* Make sure the coefficients for the rgb to gray conversion are set
-    * appropriately.
-    */
-   if (png_ptr->transformations & PNG_RGB_TO_GRAY)
-      png_colorspace_set_rgb_coefficients(png_ptr);
-#endif
 
 #ifdef PNG_READ_GRAY_TO_RGB_SUPPORTED
-#if defined(PNG_READ_EXPAND_SUPPORTED) && defined(PNG_READ_BACKGROUND_SUPPORTED)
-   /* Detect gray background and attempt to enable optimization for
-    * gray --> RGB case.
+   /* Detect gray background and attempt to enable optimization
+    * for gray --> RGB case
     *
     * Note:  if PNG_BACKGROUND_EXPAND is set and color_type is either RGB or
     * RGB_ALPHA (in which case need_expand is superfluous anyway), the
     * background color might actually be gray yet not be flagged as such.
     * This is not a problem for the current code, which uses
     * PNG_BACKGROUND_IS_GRAY only to decide when to do the
     * png_do_gray_to_rgb() transformation.
-    *
-    * TODO: this code needs to be revised to avoid the complexity and
-    * interdependencies.  The color type of the background should be recorded in
-    * png_set_background, along with the bit depth, then the code has a record
-    * of exactly what color space the background is currently in.
     */
-   if (png_ptr->transformations & PNG_BACKGROUND_EXPAND)
-   {
-      /* PNG_BACKGROUND_EXPAND: the background is in the file color space, so if
-       * the file was grayscale the background value is gray.
-       */
-      if (!(png_ptr->color_type & PNG_COLOR_MASK_COLOR))
-         png_ptr->mode |= PNG_BACKGROUND_IS_GRAY;
-   }
-
-   else if (png_ptr->transformations & PNG_COMPOSE)
-   {
-      /* PNG_COMPOSE: png_set_background was called with need_expand false,
-       * so the color is in the color space of the output or png_set_alpha_mode
-       * was called and the color is black.  Ignore RGB_TO_GRAY because that
-       * happens before GRAY_TO_RGB.
-       */
-      if (png_ptr->transformations & PNG_GRAY_TO_RGB)
-      {
-         if (png_ptr->background.red == png_ptr->background.green &&
-             png_ptr->background.red == png_ptr->background.blue)
+   if ((png_ptr->transformations & PNG_BACKGROUND_EXPAND) &&
+       !(color_type & PNG_COLOR_MASK_COLOR))
+   {
+          png_ptr->mode |= PNG_BACKGROUND_IS_GRAY;
+   } else if ((png_ptr->transformations & PNG_BACKGROUND) &&
+              !(png_ptr->transformations & PNG_BACKGROUND_EXPAND) &&
+              (png_ptr->transformations & PNG_GRAY_TO_RGB) &&
+              png_ptr->background.red == png_ptr->background.green &&
+              png_ptr->background.red == png_ptr->background.blue)
+   {
+          png_ptr->mode |= PNG_BACKGROUND_IS_GRAY;
+          png_ptr->background.gray = png_ptr->background.red;
+   }
+#endif
+
+   if ((png_ptr->transformations & PNG_BACKGROUND_EXPAND) &&
+       (png_ptr->transformations & PNG_EXPAND))
+   {
+      if (!(color_type & PNG_COLOR_MASK_COLOR))  /* i.e., GRAY or GRAY_ALPHA */
+      {
+         /* Expand background and tRNS chunks */
+         switch (png_ptr->bit_depth)
          {
-            png_ptr->mode |= PNG_BACKGROUND_IS_GRAY;
-            png_ptr->background.gray = png_ptr->background.red;
+            case 1:
+               png_ptr->background.gray *= (png_uint_16)0xff;
+               png_ptr->background.red = png_ptr->background.green
+                 =  png_ptr->background.blue = png_ptr->background.gray;
+               if (!(png_ptr->transformations & PNG_EXPAND_tRNS))
+               {
+                 png_ptr->trans_values.gray *= (png_uint_16)0xff;
+                 png_ptr->trans_values.red = png_ptr->trans_values.green
+                   = png_ptr->trans_values.blue = png_ptr->trans_values.gray;
+               }
+               break;
+
+            case 2:
+               png_ptr->background.gray *= (png_uint_16)0x55;
+               png_ptr->background.red = png_ptr->background.green
+                 = png_ptr->background.blue = png_ptr->background.gray;
+               if (!(png_ptr->transformations & PNG_EXPAND_tRNS))
+               {
+                 png_ptr->trans_values.gray *= (png_uint_16)0x55;
+                 png_ptr->trans_values.red = png_ptr->trans_values.green
+                   = png_ptr->trans_values.blue = png_ptr->trans_values.gray;
+               }
+               break;
+
+            case 4:
+               png_ptr->background.gray *= (png_uint_16)0x11;
+               png_ptr->background.red = png_ptr->background.green
+                 = png_ptr->background.blue = png_ptr->background.gray;
+               if (!(png_ptr->transformations & PNG_EXPAND_tRNS))
+               {
+                 png_ptr->trans_values.gray *= (png_uint_16)0x11;
+                 png_ptr->trans_values.red = png_ptr->trans_values.green
+                   = png_ptr->trans_values.blue = png_ptr->trans_values.gray;
+               }
+               break;
+
+            case 8:
+
+            case 16:
+               png_ptr->background.red = png_ptr->background.green
+                 = png_ptr->background.blue = png_ptr->background.gray;
+               break;
          }
       }
-   }
-#endif /* PNG_READ_EXPAND_SUPPORTED && PNG_READ_BACKGROUND_SUPPORTED */
-#endif /* PNG_READ_GRAY_TO_RGB_SUPPORTED */
-
-   /* For indexed PNG data (PNG_COLOR_TYPE_PALETTE) many of the transformations
-    * can be performed directly on the palette, and some (such as rgb to gray)
-    * can be optimized inside the palette.  This is particularly true of the
-    * composite (background and alpha) stuff, which can be pretty much all done
-    * in the palette even if the result is expanded to RGB or gray afterward.
-    *
-    * NOTE: this is Not Yet Implemented, the code behaves as in 1.5.1 and
-    * earlier and the palette stuff is actually handled on the first row.  This
-    * leads to the reported bug that the palette returned by png_get_PLTE is not
-    * updated.
-    */
-   if (png_ptr->color_type == PNG_COLOR_TYPE_PALETTE)
-      png_init_palette_transformations(png_ptr);
-
-   else
-      png_init_rgb_transformations(png_ptr);
-
-#if defined(PNG_READ_BACKGROUND_SUPPORTED) && \
-   defined(PNG_READ_EXPAND_16_SUPPORTED)
-   if ((png_ptr->transformations & PNG_EXPAND_16) &&
-      (png_ptr->transformations & PNG_COMPOSE) &&
-      !(png_ptr->transformations & PNG_BACKGROUND_EXPAND) &&
-      png_ptr->bit_depth != 16)
-   {
-      /* TODO: fix this.  Because the expand_16 operation is after the compose
-       * handling the background color must be 8, not 16, bits deep, but the
-       * application will supply a 16-bit value so reduce it here.
-       *
-       * The PNG_BACKGROUND_EXPAND code above does not expand to 16 bits at
-       * present, so that case is ok (until do_expand_16 is moved.)
-       *
-       * NOTE: this discards the low 16 bits of the user supplied background
-       * color, but until expand_16 works properly there is no choice!
-       */
-#     define CHOP(x) (x)=((png_uint_16)PNG_DIV257(x))
-      CHOP(png_ptr->background.red);
-      CHOP(png_ptr->background.green);
-      CHOP(png_ptr->background.blue);
-      CHOP(png_ptr->background.gray);
-#     undef CHOP
-   }
-#endif /* PNG_READ_BACKGROUND_SUPPORTED && PNG_READ_EXPAND_16_SUPPORTED */
-
-#if defined(PNG_READ_BACKGROUND_SUPPORTED) && \
-   (defined(PNG_READ_SCALE_16_TO_8_SUPPORTED) || \
-   defined(PNG_READ_STRIP_16_TO_8_SUPPORTED))
-   if ((png_ptr->transformations & (PNG_16_TO_8|PNG_SCALE_16_TO_8)) &&
-      (png_ptr->transformations & PNG_COMPOSE) &&
-      !(png_ptr->transformations & PNG_BACKGROUND_EXPAND) &&
-      png_ptr->bit_depth == 16)
-   {
-      /* On the other hand, if a 16-bit file is to be reduced to 8-bits per
-       * component this will also happen after PNG_COMPOSE and so the background
-       * color must be pre-expanded here.
-       *
-       * TODO: fix this too.
-       */
-      png_ptr->background.red = (png_uint_16)(png_ptr->background.red * 257);
-      png_ptr->background.green =
-         (png_uint_16)(png_ptr->background.green * 257);
-      png_ptr->background.blue = (png_uint_16)(png_ptr->background.blue * 257);
-      png_ptr->background.gray = (png_uint_16)(png_ptr->background.gray * 257);
-   }
-#endif
-
-   /* NOTE: below 'PNG_READ_ALPHA_MODE_SUPPORTED' is presumed to also enable the
-    * background support (see the comments in scripts/pnglibconf.dfa), this
-    * allows pre-multiplication of the alpha channel to be implemented as
-    * compositing on black.  This is probably sub-optimal and has been done in
-    * 1.5.4 betas simply to enable external critique and testing (i.e. to
-    * implement the new API quickly, without lots of internal changes.)
-    */
-
-#ifdef PNG_READ_GAMMA_SUPPORTED
-#  ifdef PNG_READ_BACKGROUND_SUPPORTED
-      /* Includes ALPHA_MODE */
-      png_ptr->background_1 = png_ptr->background;
-#  endif
-
-   /* This needs to change - in the palette image case a whole set of tables are
-    * built when it would be quicker to just calculate the correct value for
-    * each palette entry directly.  Also, the test is too tricky - why check
-    * PNG_RGB_TO_GRAY if PNG_GAMMA is not set?  The answer seems to be that
-    * PNG_GAMMA is cancelled even if the gamma is known?  The test excludes the
-    * PNG_COMPOSE case, so apparently if there is no *overall* gamma correction
-    * the gamma tables will not be built even if composition is required on a
-    * gamma encoded value.
-    *
-    * In 1.5.4 this is addressed below by an additional check on the individual
-    * file gamma - if it is not 1.0 both RGB_TO_GRAY and COMPOSE need the
-    * tables.
-    */
-   if ((png_ptr->transformations & PNG_GAMMA)
-      || ((png_ptr->transformations & PNG_RGB_TO_GRAY)
-         && (png_gamma_significant(png_ptr->colorspace.gamma) ||
-            png_gamma_significant(png_ptr->screen_gamma)))
-      || ((png_ptr->transformations & PNG_COMPOSE)
-         && (png_gamma_significant(png_ptr->colorspace.gamma)
-            || png_gamma_significant(png_ptr->screen_gamma)
-#  ifdef PNG_READ_BACKGROUND_SUPPORTED
-            || (png_ptr->background_gamma_type == PNG_BACKGROUND_GAMMA_UNIQUE
-               && png_gamma_significant(png_ptr->background_gamma))
-#  endif
-      )) || ((png_ptr->transformations & PNG_ENCODE_ALPHA)
-         && png_gamma_significant(png_ptr->screen_gamma))
-      )
-   {
-      png_build_gamma_table(png_ptr, png_ptr->bit_depth);
+      else if (color_type == PNG_COLOR_TYPE_PALETTE)
+      {
+         png_ptr->background.red   =
+            png_ptr->palette[png_ptr->background.index].red;
+         png_ptr->background.green =
+            png_ptr->palette[png_ptr->background.index].green;
+         png_ptr->background.blue  =
+            png_ptr->palette[png_ptr->background.index].blue;
+
+#ifdef PNG_READ_INVERT_ALPHA_SUPPORTED
+        if (png_ptr->transformations & PNG_INVERT_ALPHA)
+        {
+#ifdef PNG_READ_EXPAND_SUPPORTED
+           if (!(png_ptr->transformations & PNG_EXPAND_tRNS))
+#endif
+           {
+           /* Invert the alpha channel (in tRNS) unless the pixels are
+            * going to be expanded, in which case leave it for later
+            */
+              int i, istop;
+              istop=(int)png_ptr->num_trans;
+              for (i=0; i<istop; i++)
+                 png_ptr->trans[i] = (png_byte)(255 - png_ptr->trans[i]);
+           }
+        }
+#endif
+
+      }
+   }
+#endif
+
+#if defined(PNG_READ_BACKGROUND_SUPPORTED) && defined(PNG_READ_GAMMA_SUPPORTED)
+   png_ptr->background_1 = png_ptr->background;
+#endif
+#if defined(PNG_READ_GAMMA_SUPPORTED) && defined(PNG_FLOATING_POINT_SUPPORTED)
+
+   if ((color_type == PNG_COLOR_TYPE_PALETTE && png_ptr->num_trans != 0)
+       && (fabs(png_ptr->screen_gamma * png_ptr->gamma - 1.0)
+         < PNG_GAMMA_THRESHOLD))
+   {
+    int i, k;
+    k=0;
+    for (i=0; i<png_ptr->num_trans; i++)
+    {
+      if (png_ptr->trans[i] != 0 && png_ptr->trans[i] != 0xff)
+        k=1; /* Partial transparency is present */
+    }
+    if (k == 0)
+      png_ptr->transformations &= ~PNG_GAMMA;
+   }
+
+   if ((png_ptr->transformations & (PNG_GAMMA | PNG_RGB_TO_GRAY)) &&
+        png_ptr->gamma != 0.0)
+   {
+      png_build_gamma_table(png_ptr);
 
 #ifdef PNG_READ_BACKGROUND_SUPPORTED
-      if (png_ptr->transformations & PNG_COMPOSE)
-      {
-         /* Issue a warning about this combination: because RGB_TO_GRAY is
-          * optimized to do the gamma transform if present yet do_background has
-          * to do the same thing if both options are set a
-          * double-gamma-correction happens.  This is true in all versions of
-          * libpng to date.
-          */
-         if (png_ptr->transformations & PNG_RGB_TO_GRAY)
-            png_warning(png_ptr,
-               "libpng does not support gamma+background+rgb_to_gray");
-
-         if (png_ptr->color_type == PNG_COLOR_TYPE_PALETTE)
+      if (png_ptr->transformations & PNG_BACKGROUND)
+      {
+         if (color_type == PNG_COLOR_TYPE_PALETTE)
          {
-            /* We don't get to here unless there is a tRNS chunk with non-opaque
-             * entries - see the checking code at the start of this function.
-             */
+           /* Could skip if no transparency */
             png_color back, back_1;
             png_colorp palette = png_ptr->palette;
             int num_palette = png_ptr->num_palette;
             int i;
             if (png_ptr->background_gamma_type == PNG_BACKGROUND_GAMMA_FILE)
             {
-
                back.red = png_ptr->gamma_table[png_ptr->background.red];
                back.green = png_ptr->gamma_table[png_ptr->background.green];
                back.blue = png_ptr->gamma_table[png_ptr->background.blue];
 
                back_1.red = png_ptr->gamma_to_1[png_ptr->background.red];
                back_1.green = png_ptr->gamma_to_1[png_ptr->background.green];
                back_1.blue = png_ptr->gamma_to_1[png_ptr->background.blue];
             }
             else
             {
-               png_fixed_point g, gs;
+               double g, gs;
 
                switch (png_ptr->background_gamma_type)
                {
                   case PNG_BACKGROUND_GAMMA_SCREEN:
                      g = (png_ptr->screen_gamma);
-                     gs = PNG_FP_1;
+                     gs = 1.0;
                      break;
 
                   case PNG_BACKGROUND_GAMMA_FILE:
-                     g = png_reciprocal(png_ptr->colorspace.gamma);
-                     gs = png_reciprocal2(png_ptr->colorspace.gamma,
-                        png_ptr->screen_gamma);
+                     g = 1.0 / (png_ptr->gamma);
+                     gs = 1.0 / (png_ptr->gamma * png_ptr->screen_gamma);
                      break;
 
                   case PNG_BACKGROUND_GAMMA_UNIQUE:
-                     g = png_reciprocal(png_ptr->background_gamma);
-                     gs = png_reciprocal2(png_ptr->background_gamma,
-                        png_ptr->screen_gamma);
+                     g = 1.0 / (png_ptr->background_gamma);
+                     gs = 1.0 / (png_ptr->background_gamma *
+                                 png_ptr->screen_gamma);
                      break;
                   default:
-                     g = PNG_FP_1;    /* back_1 */
-                     gs = PNG_FP_1;   /* back */
-                     break;
+                     g = 1.0;    /* back_1 */
+                     gs = 1.0;   /* back */
                }
 
-               if (png_gamma_significant(gs))
-               {
-                  back.red = png_gamma_8bit_correct(png_ptr->background.red,
-                      gs);
-                  back.green = png_gamma_8bit_correct(png_ptr->background.green,
-                      gs);
-                  back.blue = png_gamma_8bit_correct(png_ptr->background.blue,
-                      gs);
-               }
-
-               else
+               if ( fabs(gs - 1.0) < PNG_GAMMA_THRESHOLD)
                {
                   back.red   = (png_byte)png_ptr->background.red;
                   back.green = (png_byte)png_ptr->background.green;
                   back.blue  = (png_byte)png_ptr->background.blue;
                }
-
-               if (png_gamma_significant(g))
+               else
                {
-                  back_1.red = png_gamma_8bit_correct(png_ptr->background.red,
-                     g);
-                  back_1.green = png_gamma_8bit_correct(
-                     png_ptr->background.green, g);
-                  back_1.blue = png_gamma_8bit_correct(png_ptr->background.blue,
-                     g);
+                  back.red = (png_byte)(pow(
+                     (double)png_ptr->background.red/255, gs) * 255.0 + .5);
+                  back.green = (png_byte)(pow(
+                     (double)png_ptr->background.green/255, gs) * 255.0
+                         + .5);
+                  back.blue = (png_byte)(pow(
+                     (double)png_ptr->background.blue/255, gs) * 255.0 + .5);
                }
 
-               else
-               {
-                  back_1.red   = (png_byte)png_ptr->background.red;
-                  back_1.green = (png_byte)png_ptr->background.green;
-                  back_1.blue  = (png_byte)png_ptr->background.blue;
-               }
+               back_1.red = (png_byte)(pow(
+                  (double)png_ptr->background.red/255, g) * 255.0 + .5);
+               back_1.green = (png_byte)(pow(
+                  (double)png_ptr->background.green/255, g) * 255.0 + .5);
+               back_1.blue = (png_byte)(pow(
+                  (double)png_ptr->background.blue/255, g) * 255.0 + .5);
             }
-
             for (i = 0; i < num_palette; i++)
             {
-               if (i < (int)png_ptr->num_trans &&
-                   png_ptr->trans_alpha[i] != 0xff)
+               if (i < (int)png_ptr->num_trans && png_ptr->trans[i] != 0xff)
                {
-                  if (png_ptr->trans_alpha[i] == 0)
+                  if (png_ptr->trans[i] == 0)
                   {
                      palette[i] = back;
                   }
-                  else /* if (png_ptr->trans_alpha[i] != 0xff) */
+                  else /* if (png_ptr->trans[i] != 0xff) */
                   {
                      png_byte v, w;
 
                      v = png_ptr->gamma_to_1[palette[i].red];
-                     png_composite(w, v, png_ptr->trans_alpha[i], back_1.red);
+                     png_composite(w, v, png_ptr->trans[i], back_1.red);
                      palette[i].red = png_ptr->gamma_from_1[w];
 
                      v = png_ptr->gamma_to_1[palette[i].green];
-                     png_composite(w, v, png_ptr->trans_alpha[i], back_1.green);
+                     png_composite(w, v, png_ptr->trans[i], back_1.green);
                      palette[i].green = png_ptr->gamma_from_1[w];
 
                      v = png_ptr->gamma_to_1[palette[i].blue];
-                     png_composite(w, v, png_ptr->trans_alpha[i], back_1.blue);
+                     png_composite(w, v, png_ptr->trans[i], back_1.blue);
                      palette[i].blue = png_ptr->gamma_from_1[w];
                   }
                }
                else
                {
                   palette[i].red = png_ptr->gamma_table[palette[i].red];
                   palette[i].green = png_ptr->gamma_table[palette[i].green];
                   palette[i].blue = png_ptr->gamma_table[palette[i].blue];
                }
             }
-
-            /* Prevent the transformations being done again.
-             *
-             * NOTE: this is highly dubious; it removes the transformations in
-             * place.  This seems inconsistent with the general treatment of the
-             * transformations elsewhere.
+            /* Prevent the transformations being done again, and make sure
+             * that the now spurious alpha channel is stripped - the code
+             * has just reduced background composition and gamma correction
+             * to a simple alpha channel strip.
              */
-            png_ptr->transformations &= ~(PNG_COMPOSE | PNG_GAMMA);
-         } /* color_type == PNG_COLOR_TYPE_PALETTE */
-
+            png_ptr->transformations &= ~PNG_BACKGROUND;
+            png_ptr->transformations &= ~PNG_GAMMA;
+            png_ptr->transformations |= PNG_STRIP_ALPHA;
+         }
          /* if (png_ptr->background_gamma_type!=PNG_BACKGROUND_GAMMA_UNKNOWN) */
-         else /* color_type != PNG_COLOR_TYPE_PALETTE */
+         else
+         /* color_type != PNG_COLOR_TYPE_PALETTE */
          {
-            int gs_sig, g_sig;
-            png_fixed_point g = PNG_FP_1;  /* Correction to linear */
-            png_fixed_point gs = PNG_FP_1; /* Correction to screen */
+            double m = (double)(((png_uint_32)1 << png_ptr->bit_depth) - 1);
+            double g = 1.0;
+            double gs = 1.0;
 
             switch (png_ptr->background_gamma_type)
             {
                case PNG_BACKGROUND_GAMMA_SCREEN:
-                  g = png_ptr->screen_gamma;
-                  /* gs = PNG_FP_1; */
+                  g = (png_ptr->screen_gamma);
+                  gs = 1.0;
                   break;
 
                case PNG_BACKGROUND_GAMMA_FILE:
-                  g = png_reciprocal(png_ptr->colorspace.gamma);
-                  gs = png_reciprocal2(png_ptr->colorspace.gamma,
-                     png_ptr->screen_gamma);
+                  g = 1.0 / (png_ptr->gamma);
+                  gs = 1.0 / (png_ptr->gamma * png_ptr->screen_gamma);
                   break;
 
                case PNG_BACKGROUND_GAMMA_UNIQUE:
-                  g = png_reciprocal(png_ptr->background_gamma);
-                  gs = png_reciprocal2(png_ptr->background_gamma,
-                      png_ptr->screen_gamma);
+                  g = 1.0 / (png_ptr->background_gamma);
+                  gs = 1.0 / (png_ptr->background_gamma *
+                     png_ptr->screen_gamma);
                   break;
-
-               default:
-                  png_error(png_ptr, "invalid background gamma type");
             }
 
-            g_sig = png_gamma_significant(g);
-            gs_sig = png_gamma_significant(gs);
-
-            if (g_sig)
-               png_ptr->background_1.gray = png_gamma_correct(png_ptr,
-                   png_ptr->background.gray, g);
-
-            if (gs_sig)
-               png_ptr->background.gray = png_gamma_correct(png_ptr,
-                   png_ptr->background.gray, gs);
+            png_ptr->background_1.gray = (png_uint_16)(pow(
+               (double)png_ptr->background.gray / m, g) * m + .5);
+            png_ptr->background.gray = (png_uint_16)(pow(
+               (double)png_ptr->background.gray / m, gs) * m + .5);
 
             if ((png_ptr->background.red != png_ptr->background.green) ||
                 (png_ptr->background.red != png_ptr->background.blue) ||
                 (png_ptr->background.red != png_ptr->background.gray))
             {
                /* RGB or RGBA with color background */
-               if (g_sig)
-               {
-                  png_ptr->background_1.red = png_gamma_correct(png_ptr,
-                      png_ptr->background.red, g);
-
-                  png_ptr->background_1.green = png_gamma_correct(png_ptr,
-                      png_ptr->background.green, g);
-
-                  png_ptr->background_1.blue = png_gamma_correct(png_ptr,
-                      png_ptr->background.blue, g);
-               }
-
-               if (gs_sig)
-               {
-                  png_ptr->background.red = png_gamma_correct(png_ptr,
-                      png_ptr->background.red, gs);
-
-                  png_ptr->background.green = png_gamma_correct(png_ptr,
-                      png_ptr->background.green, gs);
-
-                  png_ptr->background.blue = png_gamma_correct(png_ptr,
-                      png_ptr->background.blue, gs);
-               }
+               png_ptr->background_1.red = (png_uint_16)(pow(
+                  (double)png_ptr->background.red / m, g) * m + .5);
+               png_ptr->background_1.green = (png_uint_16)(pow(
+                  (double)png_ptr->background.green / m, g) * m + .5);
+               png_ptr->background_1.blue = (png_uint_16)(pow(
+                  (double)png_ptr->background.blue / m, g) * m + .5);
+               png_ptr->background.red = (png_uint_16)(pow(
+                  (double)png_ptr->background.red / m, gs) * m + .5);
+               png_ptr->background.green = (png_uint_16)(pow(
+                  (double)png_ptr->background.green / m, gs) * m + .5);
+               png_ptr->background.blue = (png_uint_16)(pow(
+                  (double)png_ptr->background.blue / m, gs) * m + .5);
             }
-
             else
             {
                /* GRAY, GRAY ALPHA, RGB, or RGBA with gray background */
                png_ptr->background_1.red = png_ptr->background_1.green
-                   = png_ptr->background_1.blue = png_ptr->background_1.gray;
-
+                 = png_ptr->background_1.blue = png_ptr->background_1.gray;
                png_ptr->background.red = png_ptr->background.green
-                   = png_ptr->background.blue = png_ptr->background.gray;
+                 = png_ptr->background.blue = png_ptr->background.gray;
             }
-
-            /* The background is now in screen gamma: */
-            png_ptr->background_gamma_type = PNG_BACKGROUND_GAMMA_SCREEN;
-         } /* color_type != PNG_COLOR_TYPE_PALETTE */
-      }/* png_ptr->transformations & PNG_BACKGROUND */
-
+         }
+      }
       else
       /* Transformation does not include PNG_BACKGROUND */
 #endif /* PNG_READ_BACKGROUND_SUPPORTED */
-      if (png_ptr->color_type == PNG_COLOR_TYPE_PALETTE
-#ifdef PNG_READ_RGB_TO_GRAY_SUPPORTED
-         /* RGB_TO_GRAY needs to have non-gamma-corrected values! */
-         && ((png_ptr->transformations & PNG_EXPAND) == 0 ||
-         (png_ptr->transformations & PNG_RGB_TO_GRAY) == 0)
-#endif
-         )
+      if (color_type == PNG_COLOR_TYPE_PALETTE)
       {
          png_colorp palette = png_ptr->palette;
          int num_palette = png_ptr->num_palette;
          int i;
 
-         /* NOTE: there are other transformations that should probably be in
-          * here too.
-          */
          for (i = 0; i < num_palette; i++)
          {
             palette[i].red = png_ptr->gamma_table[palette[i].red];
             palette[i].green = png_ptr->gamma_table[palette[i].green];
             palette[i].blue = png_ptr->gamma_table[palette[i].blue];
          }
 
          /* Done the gamma correction. */
          png_ptr->transformations &= ~PNG_GAMMA;
-      } /* color_type == PALETTE && !PNG_BACKGROUND transformation */
+      }
    }
 #ifdef PNG_READ_BACKGROUND_SUPPORTED
    else
 #endif
-#endif /* PNG_READ_GAMMA_SUPPORTED */
-
+#endif /* PNG_READ_GAMMA_SUPPORTED && PNG_FLOATING_POINT_SUPPORTED */
 #ifdef PNG_READ_BACKGROUND_SUPPORTED
-   /* No GAMMA transformation (see the hanging else 4 lines above) */
-   if ((png_ptr->transformations & PNG_COMPOSE) &&
-       (png_ptr->color_type == PNG_COLOR_TYPE_PALETTE))
+   /* No GAMMA transformation */
+   if ((png_ptr->transformations & PNG_BACKGROUND) &&
+       (color_type == PNG_COLOR_TYPE_PALETTE))
    {
       int i;
       int istop = (int)png_ptr->num_trans;
       png_color back;
       png_colorp palette = png_ptr->palette;
 
       back.red   = (png_byte)png_ptr->background.red;
       back.green = (png_byte)png_ptr->background.green;
       back.blue  = (png_byte)png_ptr->background.blue;
 
       for (i = 0; i < istop; i++)
       {
-         if (png_ptr->trans_alpha[i] == 0)
+         if (png_ptr->trans[i] == 0)
          {
             palette[i] = back;
          }
-
-         else if (png_ptr->trans_alpha[i] != 0xff)
+         else if (png_ptr->trans[i] != 0xff)
          {
             /* The png_composite() macro is defined in png.h */
             png_composite(palette[i].red, palette[i].red,
-                png_ptr->trans_alpha[i], back.red);
-
+               png_ptr->trans[i], back.red);
             png_composite(palette[i].green, palette[i].green,
-                png_ptr->trans_alpha[i], back.green);
-
+               png_ptr->trans[i], back.green);
             png_composite(palette[i].blue, palette[i].blue,
-                png_ptr->trans_alpha[i], back.blue);
+               png_ptr->trans[i], back.blue);
          }
       }
 
-      png_ptr->transformations &= ~PNG_COMPOSE;
+      /* Handled alpha, still need to strip the channel. */
+      png_ptr->transformations &= ~PNG_BACKGROUND;
+      png_ptr->transformations |= PNG_STRIP_ALPHA;
    }
 #endif /* PNG_READ_BACKGROUND_SUPPORTED */
 
 #ifdef PNG_READ_SHIFT_SUPPORTED
    if ((png_ptr->transformations & PNG_SHIFT) &&
-      !(png_ptr->transformations & PNG_EXPAND) &&
-       (png_ptr->color_type == PNG_COLOR_TYPE_PALETTE))
+      (color_type == PNG_COLOR_TYPE_PALETTE))
    {
-      int i;
-      int istop = png_ptr->num_palette;
-      int shift = 8 - png_ptr->sig_bit.red;
+      png_uint_16 i;
+      png_uint_16 istop = png_ptr->num_palette;
+      int sr = 8 - png_ptr->sig_bit.red;
+      int sg = 8 - png_ptr->sig_bit.green;
+      int sb = 8 - png_ptr->sig_bit.blue;
 
-      png_ptr->transformations &= ~PNG_SHIFT;
-
-      /* significant bits can be in the range 1 to 7 for a meaninful result, if
-       * the number of significant bits is 0 then no shift is done (this is an
-       * error condition which is silently ignored.)
-       */
-      if (shift > 0 && shift < 8) for (i=0; i<istop; ++i)
+      if (sr < 0 || sr > 8)
+         sr = 0;
+      if (sg < 0 || sg > 8)
+         sg = 0;
+      if (sb < 0 || sb > 8)
+         sb = 0;
+      for (i = 0; i < istop; i++)
       {
-         int component = png_ptr->palette[i].red;
-
-         component >>= shift;
-         png_ptr->palette[i].red = (png_byte)component;
-      }
-
-      shift = 8 - png_ptr->sig_bit.green;
-      if (shift > 0 && shift < 8) for (i=0; i<istop; ++i)
-      {
-         int component = png_ptr->palette[i].green;
-
-         component >>= shift;
-         png_ptr->palette[i].green = (png_byte)component;
-      }
-
-      shift = 8 - png_ptr->sig_bit.blue;
-      if (shift > 0 && shift < 8) for (i=0; i<istop; ++i)
-      {
-         int component = png_ptr->palette[i].blue;
-
-         component >>= shift;
-         png_ptr->palette[i].blue = (png_byte)component;
+         png_ptr->palette[i].red >>= sr;
+         png_ptr->palette[i].green >>= sg;
+         png_ptr->palette[i].blue >>= sb;
       }
    }
 #endif  /* PNG_READ_SHIFT_SUPPORTED */
+ }
+#if !defined(PNG_READ_GAMMA_SUPPORTED) && !defined(PNG_READ_SHIFT_SUPPORTED) \
+ && !defined(PNG_READ_BACKGROUND_SUPPORTED)
+   if (png_ptr)
+      return;
+#endif
 }
 
 /* Modify the info structure to reflect the transformations.  The
  * info should be updated so a PNG file could be written with it,
  * assuming the transformations result in valid PNG data.
  */
 void /* PRIVATE */
-png_read_transform_info(png_structrp png_ptr, png_inforp info_ptr)
+png_read_transform_info(png_structp png_ptr, png_infop info_ptr)
 {
    png_debug(1, "in png_read_transform_info");
 
 #ifdef PNG_READ_EXPAND_SUPPORTED
    if (png_ptr->transformations & PNG_EXPAND)
    {
       if (info_ptr->color_type == PNG_COLOR_TYPE_PALETTE)
       {
-         /* This check must match what actually happens in
-          * png_do_expand_palette; if it ever checks the tRNS chunk to see if
-          * it is all opaque we must do the same (at present it does not.)
-          */
-         if (png_ptr->num_trans > 0)
+         if (png_ptr->num_trans)
             info_ptr->color_type = PNG_COLOR_TYPE_RGB_ALPHA;
-
          else
             info_ptr->color_type = PNG_COLOR_TYPE_RGB;
-
          info_ptr->bit_depth = 8;
          info_ptr->num_trans = 0;
       }
       else
       {
          if (png_ptr->num_trans)
          {
             if (png_ptr->transformations & PNG_EXPAND_tRNS)
-               info_ptr->color_type |= PNG_COLOR_MASK_ALPHA;
+              info_ptr->color_type |= PNG_COLOR_MASK_ALPHA;
          }
          if (info_ptr->bit_depth < 8)
             info_ptr->bit_depth = 8;
-
          info_ptr->num_trans = 0;
       }
    }
 #endif
 
-#if defined(PNG_READ_BACKGROUND_SUPPORTED) ||\
-   defined(PNG_READ_ALPHA_MODE_SUPPORTED)
-   /* The following is almost certainly wrong unless the background value is in
-    * the screen space!
-    */
-   if (png_ptr->transformations & PNG_COMPOSE)
+#ifdef PNG_READ_BACKGROUND_SUPPORTED
+   if (png_ptr->transformations & PNG_BACKGROUND)
+   {
+      info_ptr->color_type &= ~PNG_COLOR_MASK_ALPHA;
+      info_ptr->num_trans = 0;
       info_ptr->background = png_ptr->background;
+   }
 #endif
 
 #ifdef PNG_READ_GAMMA_SUPPORTED
-   /* The following used to be conditional on PNG_GAMMA (prior to 1.5.4),
-    * however it seems that the code in png_init_read_transformations, which has
-    * been called before this from png_read_update_info->png_read_start_row
-    * sometimes does the gamma transform and cancels the flag.
-    *
-    * TODO: this looks wrong; the info_ptr should end up with a gamma equal to
-    * the screen_gamma value.  The following probably results in weirdness if
-    * the info_ptr is used by the app after the rows have been read.
-    */
-   info_ptr->colorspace.gamma = png_ptr->colorspace.gamma;
+   if (png_ptr->transformations & PNG_GAMMA)
+   {
+#ifdef PNG_FLOATING_POINT_SUPPORTED
+      info_ptr->gamma = png_ptr->gamma;
+#endif
+#ifdef PNG_FIXED_POINT_SUPPORTED
+      info_ptr->int_gamma = png_ptr->int_gamma;
+#endif
+   }
 #endif
 
-   if (info_ptr->bit_depth == 16)
-   {
-#  ifdef PNG_READ_16BIT_SUPPORTED
-#     ifdef PNG_READ_SCALE_16_TO_8_SUPPORTED
-         if (png_ptr->transformations & PNG_SCALE_16_TO_8)
-            info_ptr->bit_depth = 8;
-#     endif
-
-#     ifdef PNG_READ_STRIP_16_TO_8_SUPPORTED
-         if (png_ptr->transformations & PNG_16_TO_8)
-            info_ptr->bit_depth = 8;
-#     endif
-
-#  else
-      /* No 16 bit support: force chopping 16-bit input down to 8, in this case
-       * the app program can chose if both APIs are available by setting the
-       * correct scaling to use.
-       */
-#     ifdef PNG_READ_STRIP_16_TO_8_SUPPORTED
-         /* For compatibility with previous versions use the strip method by
-          * default.  This code works because if PNG_SCALE_16_TO_8 is already
-          * set the code below will do that in preference to the chop.
-          */
-         png_ptr->transformations |= PNG_16_TO_8;
-         info_ptr->bit_depth = 8;
-#     else
-
-#        ifdef PNG_READ_SCALE_16_TO_8_SUPPORTED
-            png_ptr->transformations |= PNG_SCALE_16_TO_8;
-            info_ptr->bit_depth = 8;
-#        else
-
-            CONFIGURATION ERROR: you must enable at least one 16 to 8 method
-#        endif
-#    endif
-#endif /* !READ_16BIT_SUPPORTED */
-   }
+#ifdef PNG_READ_16_TO_8_SUPPORTED
+   if ((png_ptr->transformations & PNG_16_TO_8) && (info_ptr->bit_depth == 16))
+      info_ptr->bit_depth = 8;
+#endif
 
 #ifdef PNG_READ_GRAY_TO_RGB_SUPPORTED
    if (png_ptr->transformations & PNG_GRAY_TO_RGB)
-      info_ptr->color_type = (png_byte)(info_ptr->color_type |
-         PNG_COLOR_MASK_COLOR);
+      info_ptr->color_type |= PNG_COLOR_MASK_COLOR;
 #endif
 
 #ifdef PNG_READ_RGB_TO_GRAY_SUPPORTED
    if (png_ptr->transformations & PNG_RGB_TO_GRAY)
-      info_ptr->color_type = (png_byte)(info_ptr->color_type &
-         ~PNG_COLOR_MASK_COLOR);
+      info_ptr->color_type &= ~PNG_COLOR_MASK_COLOR;
 #endif
 
-#ifdef PNG_READ_QUANTIZE_SUPPORTED
-   if (png_ptr->transformations & PNG_QUANTIZE)
+#ifdef PNG_READ_DITHER_SUPPORTED
+   if (png_ptr->transformations & PNG_DITHER)
    {
       if (((info_ptr->color_type == PNG_COLOR_TYPE_RGB) ||
           (info_ptr->color_type == PNG_COLOR_TYPE_RGB_ALPHA)) &&
           png_ptr->palette_lookup && info_ptr->bit_depth == 8)
       {
          info_ptr->color_type = PNG_COLOR_TYPE_PALETTE;
       }
    }
 #endif
 
-#ifdef PNG_READ_EXPAND_16_SUPPORTED
-   if (png_ptr->transformations & PNG_EXPAND_16 && info_ptr->bit_depth == 8 &&
-      info_ptr->color_type != PNG_COLOR_TYPE_PALETTE)
-   {
-      info_ptr->bit_depth = 16;
-   }
-#endif
-
 #ifdef PNG_READ_PACK_SUPPORTED
    if ((png_ptr->transformations & PNG_PACK) && (info_ptr->bit_depth < 8))
       info_ptr->bit_depth = 8;
 #endif
 
    if (info_ptr->color_type == PNG_COLOR_TYPE_PALETTE)
       info_ptr->channels = 1;
-
    else if (info_ptr->color_type & PNG_COLOR_MASK_COLOR)
       info_ptr->channels = 3;
-
    else
       info_ptr->channels = 1;
 
 #ifdef PNG_READ_STRIP_ALPHA_SUPPORTED
-   if (png_ptr->transformations & PNG_STRIP_ALPHA)
-   {
-      info_ptr->color_type = (png_byte)(info_ptr->color_type &
-         ~PNG_COLOR_MASK_ALPHA);
-      info_ptr->num_trans = 0;
-   }
+   if (png_ptr->flags & PNG_FLAG_STRIP_ALPHA)
+      info_ptr->color_type &= ~PNG_COLOR_MASK_ALPHA;
 #endif
 
    if (info_ptr->color_type & PNG_COLOR_MASK_ALPHA)
       info_ptr->channels++;
 
 #ifdef PNG_READ_FILLER_SUPPORTED
    /* STRIP_ALPHA and FILLER allowed:  MASK_ALPHA bit stripped above */
    if ((png_ptr->transformations & PNG_FILLER) &&
        ((info_ptr->color_type == PNG_COLOR_TYPE_RGB) ||
        (info_ptr->color_type == PNG_COLOR_TYPE_GRAY)))
    {
       info_ptr->channels++;
       /* If adding a true alpha channel not just filler */
+#ifndef PNG_1_0_X
       if (png_ptr->transformations & PNG_ADD_ALPHA)
-         info_ptr->color_type |= PNG_COLOR_MASK_ALPHA;
+        info_ptr->color_type |= PNG_COLOR_MASK_ALPHA;
+#endif
    }
 #endif
 
 #if defined(PNG_USER_TRANSFORM_PTR_SUPPORTED) && \
 defined(PNG_READ_USER_TRANSFORM_SUPPORTED)
    if (png_ptr->transformations & PNG_USER_TRANSFORM)
-   {
-      if (info_ptr->bit_depth < png_ptr->user_transform_depth)
+     {
+       if (info_ptr->bit_depth < png_ptr->user_transform_depth)
          info_ptr->bit_depth = png_ptr->user_transform_depth;
-
-      if (info_ptr->channels < png_ptr->user_transform_channels)
+       if (info_ptr->channels < png_ptr->user_transform_channels)
          info_ptr->channels = png_ptr->user_transform_channels;
-   }
+     }
 #endif
 
    info_ptr->pixel_depth = (png_byte)(info_ptr->channels *
-       info_ptr->bit_depth);
+      info_ptr->bit_depth);
 
    info_ptr->rowbytes = PNG_ROWBYTES(info_ptr->pixel_depth, info_ptr->width);
 
-   /* Adding in 1.5.4: cache the above value in png_struct so that we can later
-    * check in png_rowbytes that the user buffer won't get overwritten.  Note
-    * that the field is not always set - if png_read_update_info isn't called
-    * the application has to either not do any transforms or get the calculation
-    * right itself.
-    */
-   png_ptr->info_rowbytes = info_ptr->rowbytes;
-
 #ifndef PNG_READ_EXPAND_SUPPORTED
    if (png_ptr)
       return;
 #endif
 }
 
 /* Transform the row.  The order of transformations is significant,
  * and is very touchy.  If you add a transformation, take care to
  * decide how it fits in with the other transformations here.
  */
 void /* PRIVATE */
-png_do_read_transformations(png_structrp png_ptr, png_row_infop row_info)
+png_do_read_transformations(png_structp png_ptr)
 {
    png_debug(1, "in png_do_read_transformations");
 
    if (png_ptr->row_buf == NULL)
    {
-      /* Prior to 1.5.4 this output row/pass where the NULL pointer is, but this
-       * error is incredibly rare and incredibly easy to debug without this
-       * information.
+#if defined(PNG_STDIO_SUPPORTED) && !defined(_WIN32_WCE)
+      char msg[50];
+
+      png_snprintf2(msg, 50,
+         "NULL row buffer for row %ld, pass %d", (long)png_ptr->row_number,
+         png_ptr->pass);
+      png_error(png_ptr, msg);
+#else
+      png_error(png_ptr, "NULL row buffer");
+#endif
+   }
+#ifdef PNG_WARN_UNINITIALIZED_ROW
+   if (!(png_ptr->flags & PNG_FLAG_ROW_INIT))
+      /* Application has failed to call either png_read_start_image()
+       * or png_read_update_info() after setting transforms that expand
+       * pixels.  This check added to libpng-1.2.19
        */
-      png_error(png_ptr, "NULL row buffer");
-   }
-
-   /* The following is debugging; prior to 1.5.4 the code was never compiled in;
-    * in 1.5.4 PNG_FLAG_DETECT_UNINITIALIZED was added and the macro
-    * PNG_WARN_UNINITIALIZED_ROW removed.  In 1.6 the new flag is set only for
-    * all transformations, however in practice the ROW_INIT always gets done on
-    * demand, if necessary.
-    */
-   if ((png_ptr->flags & PNG_FLAG_DETECT_UNINITIALIZED) != 0 &&
-      !(png_ptr->flags & PNG_FLAG_ROW_INIT))
-   {
-      /* Application has failed to call either png_read_start_image() or
-       * png_read_update_info() after setting transforms that expand pixels.
-       * This check added to libpng-1.2.19 (but not enabled until 1.5.4).
-       */
+#if (PNG_WARN_UNINITIALIZED_ROW==1)
       png_error(png_ptr, "Uninitialized row");
-   }
+#else
+      png_warning(png_ptr, "Uninitialized row");
+#endif
+#endif
 
 #ifdef PNG_READ_EXPAND_SUPPORTED
    if (png_ptr->transformations & PNG_EXPAND)
    {
-      if (row_info->color_type == PNG_COLOR_TYPE_PALETTE)
+      if (png_ptr->row_info.color_type == PNG_COLOR_TYPE_PALETTE)
       {
-         png_do_expand_palette(row_info, png_ptr->row_buf + 1,
-             png_ptr->palette, png_ptr->trans_alpha, png_ptr->num_trans);
+         png_do_expand_palette(&(png_ptr->row_info), png_ptr->row_buf + 1,
+            png_ptr->palette, png_ptr->trans, png_ptr->num_trans);
       }
-
       else
       {
          if (png_ptr->num_trans &&
              (png_ptr->transformations & PNG_EXPAND_tRNS))
-            png_do_expand(row_info, png_ptr->row_buf + 1,
-                &(png_ptr->trans_color));
-
+            png_do_expand(&(png_ptr->row_info), png_ptr->row_buf + 1,
+               &(png_ptr->trans_values));
          else
-            png_do_expand(row_info, png_ptr->row_buf + 1,
-                NULL);
+            png_do_expand(&(png_ptr->row_info), png_ptr->row_buf + 1,
+               NULL);
       }
    }
 #endif
 
 #ifdef PNG_READ_STRIP_ALPHA_SUPPORTED
-   if ((png_ptr->transformations & PNG_STRIP_ALPHA) &&
-      !(png_ptr->transformations & PNG_COMPOSE) &&
-      (row_info->color_type == PNG_COLOR_TYPE_RGB_ALPHA ||
-      row_info->color_type == PNG_COLOR_TYPE_GRAY_ALPHA))
-      png_do_strip_channel(row_info, png_ptr->row_buf + 1,
-         0 /* at_start == false, because SWAP_ALPHA happens later */);
+   if (png_ptr->flags & PNG_FLAG_STRIP_ALPHA)
+      png_do_strip_filler(&(png_ptr->row_info), png_ptr->row_buf + 1,
+         PNG_FLAG_FILLER_AFTER | (png_ptr->flags & PNG_FLAG_STRIP_ALPHA));
 #endif
 
 #ifdef PNG_READ_RGB_TO_GRAY_SUPPORTED
    if (png_ptr->transformations & PNG_RGB_TO_GRAY)
    {
       int rgb_error =
-          png_do_rgb_to_gray(png_ptr, row_info,
-              png_ptr->row_buf + 1);
-
+         png_do_rgb_to_gray(png_ptr, &(png_ptr->row_info),
+             png_ptr->row_buf + 1);
       if (rgb_error)
       {
          png_ptr->rgb_to_gray_status=1;
          if ((png_ptr->transformations & PNG_RGB_TO_GRAY) ==
              PNG_RGB_TO_GRAY_WARN)
             png_warning(png_ptr, "png_do_rgb_to_gray found nongray pixel");
-
          if ((png_ptr->transformations & PNG_RGB_TO_GRAY) ==
              PNG_RGB_TO_GRAY_ERR)
             png_error(png_ptr, "png_do_rgb_to_gray found nongray pixel");
       }
    }
 #endif
 
 /* From Andreas Dilger e-mail to png-implement, 26 March 1998:
  *
  *   In most cases, the "simple transparency" should be done prior to doing
@@ skipping 24 matching lines @@
  *  in advance if the background was gray or RGB, and position the gray-to-RGB
  *  transform appropriately, then it would save a lot of work/time.
  */
 
 #ifdef PNG_READ_GRAY_TO_RGB_SUPPORTED
    /* If gray -> RGB, do so now only if background is non-gray; else do later
     * for performance reasons
     */
    if ((png_ptr->transformations & PNG_GRAY_TO_RGB) &&
        !(png_ptr->mode & PNG_BACKGROUND_IS_GRAY))
-      png_do_gray_to_rgb(row_info, png_ptr->row_buf + 1);
+      png_do_gray_to_rgb(&(png_ptr->row_info), png_ptr->row_buf + 1);
 #endif
 
-#if defined(PNG_READ_BACKGROUND_SUPPORTED) ||\
-   defined(PNG_READ_ALPHA_MODE_SUPPORTED)
-   if (png_ptr->transformations & PNG_COMPOSE)
-      png_do_compose(row_info, png_ptr->row_buf + 1, png_ptr);
+#ifdef PNG_READ_BACKGROUND_SUPPORTED
+   if ((png_ptr->transformations & PNG_BACKGROUND) &&
+      ((png_ptr->num_trans != 0 ) ||
+      (png_ptr->color_type & PNG_COLOR_MASK_ALPHA)))
+      png_do_background(&(png_ptr->row_info), png_ptr->row_buf + 1,
+         &(png_ptr->trans_values), &(png_ptr->background)
+#ifdef PNG_READ_GAMMA_SUPPORTED
+         , &(png_ptr->background_1),
+         png_ptr->gamma_table, png_ptr->gamma_from_1,
+         png_ptr->gamma_to_1, png_ptr->gamma_16_table,
+         png_ptr->gamma_16_from_1, png_ptr->gamma_16_to_1,
+         png_ptr->gamma_shift
+#endif
+);
 #endif
 
 #ifdef PNG_READ_GAMMA_SUPPORTED
    if ((png_ptr->transformations & PNG_GAMMA) &&
-#ifdef PNG_READ_RGB_TO_GRAY_SUPPORTED
-      /* Because RGB_TO_GRAY does the gamma transform. */
-      !(png_ptr->transformations & PNG_RGB_TO_GRAY) &&
-#endif
-#if defined(PNG_READ_BACKGROUND_SUPPORTED) ||\
-   defined(PNG_READ_ALPHA_MODE_SUPPORTED)
-      /* Because PNG_COMPOSE does the gamma transform if there is something to
-       * do (if there is an alpha channel or transparency.)
-       */
-       !((png_ptr->transformations & PNG_COMPOSE) &&
+#ifdef PNG_READ_BACKGROUND_SUPPORTED
+       !((png_ptr->transformations & PNG_BACKGROUND) &&
        ((png_ptr->num_trans != 0) ||
        (png_ptr->color_type & PNG_COLOR_MASK_ALPHA))) &&
 #endif
-      /* Because png_init_read_transformations transforms the palette, unless
-       * RGB_TO_GRAY will do the transform.
-       */
        (png_ptr->color_type != PNG_COLOR_TYPE_PALETTE))
-      png_do_gamma(row_info, png_ptr->row_buf + 1, png_ptr);
+      png_do_gamma(&(png_ptr->row_info), png_ptr->row_buf + 1,
+          png_ptr->gamma_table, png_ptr->gamma_16_table,
+          png_ptr->gamma_shift);
 #endif
 
-#ifdef PNG_READ_STRIP_ALPHA_SUPPORTED
-   if ((png_ptr->transformations & PNG_STRIP_ALPHA) &&
-      (png_ptr->transformations & PNG_COMPOSE) &&
-      (row_info->color_type == PNG_COLOR_TYPE_RGB_ALPHA ||
-      row_info->color_type == PNG_COLOR_TYPE_GRAY_ALPHA))
-      png_do_strip_channel(row_info, png_ptr->row_buf + 1,
-         0 /* at_start == false, because SWAP_ALPHA happens later */);
+#ifdef PNG_READ_16_TO_8_SUPPORTED
+   if (png_ptr->transformations & PNG_16_TO_8)
+      png_do_chop(&(png_ptr->row_info), png_ptr->row_buf + 1);
 #endif
 
-#ifdef PNG_READ_ALPHA_MODE_SUPPORTED
-   if ((png_ptr->transformations & PNG_ENCODE_ALPHA) &&
-      (row_info->color_type & PNG_COLOR_MASK_ALPHA))
-      png_do_encode_alpha(row_info, png_ptr->row_buf + 1, png_ptr);
-#endif
-
-#ifdef PNG_READ_SCALE_16_TO_8_SUPPORTED
-   if (png_ptr->transformations & PNG_SCALE_16_TO_8)
-      png_do_scale_16_to_8(row_info, png_ptr->row_buf + 1);
-#endif
-
-#ifdef PNG_READ_STRIP_16_TO_8_SUPPORTED
-   /* There is no harm in doing both of these because only one has any effect,
-    * by putting the 'scale' option first if the app asks for scale (either by
-    * calling the API or in a TRANSFORM flag) this is what happens.
-    */
-   if (png_ptr->transformations & PNG_16_TO_8)
-      png_do_chop(row_info, png_ptr->row_buf + 1);
-#endif
-
-#ifdef PNG_READ_QUANTIZE_SUPPORTED
-   if (png_ptr->transformations & PNG_QUANTIZE)
+#ifdef PNG_READ_DITHER_SUPPORTED
+   if (png_ptr->transformations & PNG_DITHER)
    {
-      png_do_quantize(row_info, png_ptr->row_buf + 1,
-          png_ptr->palette_lookup, png_ptr->quantize_index);
-
-      if (row_info->rowbytes == 0)
-         png_error(png_ptr, "png_do_quantize returned rowbytes=0");
+      png_do_dither((png_row_infop)&(png_ptr->row_info), png_ptr->row_buf + 1,
+         png_ptr->palette_lookup, png_ptr->dither_index);
+      if (png_ptr->row_info.rowbytes == (png_uint_32)0)
+         png_error(png_ptr, "png_do_dither returned rowbytes=0");
    }
-#endif /* PNG_READ_QUANTIZE_SUPPORTED */
-
-#ifdef PNG_READ_EXPAND_16_SUPPORTED
-   /* Do the expansion now, after all the arithmetic has been done.  Notice
-    * that previous transformations can handle the PNG_EXPAND_16 flag if this
-    * is efficient (particularly true in the case of gamma correction, where
-    * better accuracy results faster!)
-    */
-   if (png_ptr->transformations & PNG_EXPAND_16)
-      png_do_expand_16(row_info, png_ptr->row_buf + 1);
-#endif
-
-#ifdef PNG_READ_GRAY_TO_RGB_SUPPORTED
-   /* NOTE: moved here in 1.5.4 (from much later in this list.) */
-   if ((png_ptr->transformations & PNG_GRAY_TO_RGB) &&
-       (png_ptr->mode & PNG_BACKGROUND_IS_GRAY))
-      png_do_gray_to_rgb(row_info, png_ptr->row_buf + 1);
 #endif
 
 #ifdef PNG_READ_INVERT_SUPPORTED
    if (png_ptr->transformations & PNG_INVERT_MONO)
-      png_do_invert(row_info, png_ptr->row_buf + 1);
+      png_do_invert(&(png_ptr->row_info), png_ptr->row_buf + 1);
 #endif
 
 #ifdef PNG_READ_SHIFT_SUPPORTED
    if (png_ptr->transformations & PNG_SHIFT)
-      png_do_unshift(row_info, png_ptr->row_buf + 1,
-          &(png_ptr->shift));
+      png_do_unshift(&(png_ptr->row_info), png_ptr->row_buf + 1,
+         &(png_ptr->shift));
 #endif
 
 #ifdef PNG_READ_PACK_SUPPORTED
    if (png_ptr->transformations & PNG_PACK)
-      png_do_unpack(row_info, png_ptr->row_buf + 1);
-#endif
-
-#ifdef PNG_READ_CHECK_FOR_INVALID_INDEX_SUPPORTED
-   /* Added at libpng-1.5.10 */
-   if (row_info->color_type == PNG_COLOR_TYPE_PALETTE &&
-       png_ptr->num_palette_max >= 0)
-      png_do_check_palette_indexes(png_ptr, row_info);
+      png_do_unpack(&(png_ptr->row_info), png_ptr->row_buf + 1);
 #endif
 
 #ifdef PNG_READ_BGR_SUPPORTED
    if (png_ptr->transformations & PNG_BGR)
-      png_do_bgr(row_info, png_ptr->row_buf + 1);
+      png_do_bgr(&(png_ptr->row_info), png_ptr->row_buf + 1);
 #endif
 
 #ifdef PNG_READ_PACKSWAP_SUPPORTED
    if (png_ptr->transformations & PNG_PACKSWAP)
-      png_do_packswap(row_info, png_ptr->row_buf + 1);
+      png_do_packswap(&(png_ptr->row_info), png_ptr->row_buf + 1);
+#endif
+
+#ifdef PNG_READ_GRAY_TO_RGB_SUPPORTED
+   /* If gray -> RGB, do so now only if we did not do so above */
+   if ((png_ptr->transformations & PNG_GRAY_TO_RGB) &&
+       (png_ptr->mode & PNG_BACKGROUND_IS_GRAY))
+      png_do_gray_to_rgb(&(png_ptr->row_info), png_ptr->row_buf + 1);
 #endif
 
 #ifdef PNG_READ_FILLER_SUPPORTED
    if (png_ptr->transformations & PNG_FILLER)
-      png_do_read_filler(row_info, png_ptr->row_buf + 1,
-          (png_uint_32)png_ptr->filler, png_ptr->flags);
+      png_do_read_filler(&(png_ptr->row_info), png_ptr->row_buf + 1,
+         (png_uint_32)png_ptr->filler, png_ptr->flags);
 #endif
 
 #ifdef PNG_READ_INVERT_ALPHA_SUPPORTED
    if (png_ptr->transformations & PNG_INVERT_ALPHA)
-      png_do_read_invert_alpha(row_info, png_ptr->row_buf + 1);
+      png_do_read_invert_alpha(&(png_ptr->row_info), png_ptr->row_buf + 1);
 #endif
 
 #ifdef PNG_READ_SWAP_ALPHA_SUPPORTED
    if (png_ptr->transformations & PNG_SWAP_ALPHA)
-      png_do_read_swap_alpha(row_info, png_ptr->row_buf + 1);
+      png_do_read_swap_alpha(&(png_ptr->row_info), png_ptr->row_buf + 1);
 #endif
 
-#ifdef PNG_READ_16BIT_SUPPORTED
 #ifdef PNG_READ_SWAP_SUPPORTED
    if (png_ptr->transformations & PNG_SWAP_BYTES)
-      png_do_swap(row_info, png_ptr->row_buf + 1);
-#endif
+      png_do_swap(&(png_ptr->row_info), png_ptr->row_buf + 1);
 #endif
 
 #ifdef PNG_READ_USER_TRANSFORM_SUPPORTED
    if (png_ptr->transformations & PNG_USER_TRANSFORM)
     {
       if (png_ptr->read_user_transform_fn != NULL)
          (*(png_ptr->read_user_transform_fn)) /* User read transform function */
-             (png_ptr,     /* png_ptr */
-             row_info,     /* row_info: */
-                /*  png_uint_32 width;       width of row */
-                /*  png_size_t rowbytes;     number of bytes in row */
-                /*  png_byte color_type;     color type of pixels */
-                /*  png_byte bit_depth;      bit depth of samples */
-                /*  png_byte channels;       number of channels (1-4) */
-                /*  png_byte pixel_depth;    bits per pixel (depth*channels) */
-             png_ptr->row_buf + 1);    /* start of pixel data for row */
+            (png_ptr,                    /* png_ptr */
+               &(png_ptr->row_info),     /* row_info: */
+               /*  png_uint_32 width;       width of row */
+               /*  png_uint_32 rowbytes;    number of bytes in row */
+               /*  png_byte color_type;     color type of pixels */
+               /*  png_byte bit_depth;      bit depth of samples */
+               /*  png_byte channels;       number of channels (1-4) */
+               /*  png_byte pixel_depth;    bits per pixel (depth*channels) */
+               png_ptr->row_buf + 1);    /* start of pixel data for row */
 #ifdef PNG_USER_TRANSFORM_PTR_SUPPORTED
       if (png_ptr->user_transform_depth)
-         row_info->bit_depth = png_ptr->user_transform_depth;
-
+         png_ptr->row_info.bit_depth = png_ptr->user_transform_depth;
       if (png_ptr->user_transform_channels)
-         row_info->channels = png_ptr->user_transform_channels;
+         png_ptr->row_info.channels = png_ptr->user_transform_channels;
 #endif
-      row_info->pixel_depth = (png_byte)(row_info->bit_depth *
-          row_info->channels);
-
-      row_info->rowbytes = PNG_ROWBYTES(row_info->pixel_depth, row_info->width);
+      png_ptr->row_info.pixel_depth = (png_byte)(png_ptr->row_info.bit_depth *
+         png_ptr->row_info.channels);
+      png_ptr->row_info.rowbytes = PNG_ROWBYTES(png_ptr->row_info.pixel_depth,
+         png_ptr->row_info.width);
    }
 #endif
+
 }
 
 #ifdef PNG_READ_PACK_SUPPORTED
 /* Unpack pixels of 1, 2, or 4 bits per pixel into 1 byte per pixel,
  * without changing the actual values.  Thus, if you had a row with
  * a bit depth of 1, you would end up with bytes that only contained
  * the numbers 0 or 1.  If you would rather they contain 0 and 255, use
  * png_do_shift() after this.
  */
 void /* PRIVATE */
 png_do_unpack(png_row_infop row_info, png_bytep row)
 {
    png_debug(1, "in png_do_unpack");
 
+#ifdef PNG_USELESS_TESTS_SUPPORTED
+   if (row != NULL && row_info != NULL && row_info->bit_depth < 8)
+#else
    if (row_info->bit_depth < 8)
+#endif
    {
       png_uint_32 i;
       png_uint_32 row_width=row_info->width;
 
       switch (row_info->bit_depth)
       {
          case 1:
          {
             png_bytep sp = row + (png_size_t)((row_width - 1) >> 3);
             png_bytep dp = row + (png_size_t)row_width - 1;
             png_uint_32 shift = 7 - (int)((row_width + 7) & 0x07);
             for (i = 0; i < row_width; i++)
             {
                *dp = (png_byte)((*sp >> shift) & 0x01);
-
                if (shift == 7)
                {
                   shift = 0;
                   sp--;
                }
-
                else
                   shift++;
 
                dp--;
             }
             break;
          }
 
          case 2:
          {
 
             png_bytep sp = row + (png_size_t)((row_width - 1) >> 2);
             png_bytep dp = row + (png_size_t)row_width - 1;
             png_uint_32 shift = (int)((3 - ((row_width + 3) & 0x03)) << 1);
             for (i = 0; i < row_width; i++)
             {
                *dp = (png_byte)((*sp >> shift) & 0x03);
-
                if (shift == 6)
                {
                   shift = 0;
                   sp--;
                }
-
                else
                   shift += 2;
 
                dp--;
             }
             break;
          }
 
          case 4:
          {
             png_bytep sp = row + (png_size_t)((row_width - 1) >> 1);
             png_bytep dp = row + (png_size_t)row_width - 1;
             png_uint_32 shift = (int)((1 - ((row_width + 1) & 0x01)) << 2);
             for (i = 0; i < row_width; i++)
             {
                *dp = (png_byte)((*sp >> shift) & 0x0f);
-
                if (shift == 4)
                {
                   shift = 0;
                   sp--;
                }
-
                else
                   shift = 4;
 
                dp--;
             }
             break;
          }
-
-         default:
-            break;
       }
       row_info->bit_depth = 8;
       row_info->pixel_depth = (png_byte)(8 * row_info->channels);
       row_info->rowbytes = row_width * row_info->channels;
    }
 }
 #endif
 
 #ifdef PNG_READ_SHIFT_SUPPORTED
 /* Reverse the effects of png_do_shift.  This routine merely shifts the
  * pixels back to their significant bits values.  Thus, if you have
  * a row of bit depth 8, but only 5 are significant, this will shift
  * the values back to 0 through 31.
  */
 void /* PRIVATE */
-png_do_unshift(png_row_infop row_info, png_bytep row,
-    png_const_color_8p sig_bits)
+png_do_unshift(png_row_infop row_info, png_bytep row, png_color_8p sig_bits)
 {
-   int color_type;
-
    png_debug(1, "in png_do_unshift");
 
-   /* The palette case has already been handled in the _init routine. */
-   color_type = row_info->color_type;
-
-   if (color_type != PNG_COLOR_TYPE_PALETTE)
+   if (
+#ifdef PNG_USELESS_TESTS_SUPPORTED
+       row != NULL && row_info != NULL && sig_bits != NULL &&
+#endif
+       row_info->color_type != PNG_COLOR_TYPE_PALETTE)
    {
       int shift[4];
       int channels = 0;
-      int bit_depth = row_info->bit_depth;
+      int c;
+      png_uint_16 value = 0;
+      png_uint_32 row_width = row_info->width;
 
-      if (color_type & PNG_COLOR_MASK_COLOR)
+      if (row_info->color_type & PNG_COLOR_MASK_COLOR)
       {
-         shift[channels++] = bit_depth - sig_bits->red;
-         shift[channels++] = bit_depth - sig_bits->green;
-         shift[channels++] = bit_depth - sig_bits->blue;
+         shift[channels++] = row_info->bit_depth - sig_bits->red;
+         shift[channels++] = row_info->bit_depth - sig_bits->green;
+         shift[channels++] = row_info->bit_depth - sig_bits->blue;
+      }
+      else
+      {
+         shift[channels++] = row_info->bit_depth - sig_bits->gray;
+      }
+      if (row_info->color_type & PNG_COLOR_MASK_ALPHA)
+      {
+         shift[channels++] = row_info->bit_depth - sig_bits->alpha;
       }
 
-      else
+      for (c = 0; c < channels; c++)
       {
-         shift[channels++] = bit_depth - sig_bits->gray;
+         if (shift[c] <= 0)
+            shift[c] = 0;
+         else
+            value = 1;
       }
 
-      if (color_type & PNG_COLOR_MASK_ALPHA)
+      if (!value)
+         return;
+
+      switch (row_info->bit_depth)
       {
-         shift[channels++] = bit_depth - sig_bits->alpha;
-      }
+         case 2:
+         {
+            png_bytep bp;
+            png_uint_32 i;
+            png_uint_32 istop = row_info->rowbytes;
 
-      {
-         int c, have_shift;
-
-         for (c = have_shift = 0; c < channels; ++c)
-         {
-            /* A shift of more than the bit depth is an error condition but it
-             * gets ignored here.
-             */
-            if (shift[c] <= 0 || shift[c] >= bit_depth)
-               shift[c] = 0;
-
-            else
-               have_shift = 1;
-         }
-
-         if (!have_shift)
-            return;
-      }
-
-      switch (bit_depth)
-      {
-         default:
-         /* Must be 1bpp gray: should not be here! */
-            /* NOTREACHED */
-            break;
-
-         case 2:
-         /* Must be 2bpp gray */
-         /* assert(channels == 1 && shift[0] == 1) */
-         {
-            png_bytep bp = row;
-            png_bytep bp_end = bp + row_info->rowbytes;
-
-            while (bp < bp_end)
+            for (bp = row, i = 0; i < istop; i++)
             {
-               int b = (*bp >> 1) & 0x55;
-               *bp++ = (png_byte)b;
+               *bp >>= 1;
+               *bp++ &= 0x55;
             }
             break;
          }
 
          case 4:
-         /* Must be 4bpp gray */
-         /* assert(channels == 1) */
          {
             png_bytep bp = row;
-            png_bytep bp_end = bp + row_info->rowbytes;
-            int gray_shift = shift[0];
-            int mask =  0xf >> gray_shift;
+            png_uint_32 i;
+            png_uint_32 istop = row_info->rowbytes;
+            png_byte mask = (png_byte)((((int)0xf0 >> shift[0]) & (int)0xf0) |
+               (png_byte)((int)0xf >> shift[0]));
 
-            mask |= mask << 4;
-
-            while (bp < bp_end)
+            for (i = 0; i < istop; i++)
             {
-               int b = (*bp >> gray_shift) & mask;
-               *bp++ = (png_byte)b;
+               *bp >>= shift[0];
+               *bp++ &= mask;
             }
             break;
          }
 
          case 8:
-         /* Single byte components, G, GA, RGB, RGBA */
          {
             png_bytep bp = row;
-            png_bytep bp_end = bp + row_info->rowbytes;
-            int channel = 0;
+            png_uint_32 i;
+            png_uint_32 istop = row_width * channels;
 
-            while (bp < bp_end)
+            for (i = 0; i < istop; i++)
             {
-               int b = *bp >> shift[channel];
-               if (++channel >= channels)
-                  channel = 0;
-               *bp++ = (png_byte)b;
+               *bp++ >>= shift[i%channels];
             }
             break;
          }
 
-#ifdef PNG_READ_16BIT_SUPPORTED
          case 16:
-         /* Double byte components, G, GA, RGB, RGBA */
          {
             png_bytep bp = row;
-            png_bytep bp_end = bp + row_info->rowbytes;
-            int channel = 0;
+            png_uint_32 i;
+            png_uint_32 istop = channels * row_width;
 
-            while (bp < bp_end)
+            for (i = 0; i < istop; i++)
             {
-               int value = (bp[0] << 8) + bp[1];
-
-               value >>= shift[channel];
-               if (++channel >= channels)
-                  channel = 0;
+               value = (png_uint_16)((*bp << 8) + *(bp + 1));
+               value >>= shift[i%channels];
                *bp++ = (png_byte)(value >> 8);
                *bp++ = (png_byte)(value & 0xff);
             }
             break;
          }
-#endif
       }
    }
 }
 #endif
 
-#ifdef PNG_READ_SCALE_16_TO_8_SUPPORTED
-/* Scale rows of bit depth 16 down to 8 accurately */
+#ifdef PNG_READ_16_TO_8_SUPPORTED
+/* Chop rows of bit depth 16 down to 8 */
 void /* PRIVATE */
-png_do_scale_16_to_8(png_row_infop row_info, png_bytep row)
-{
-   png_debug(1, "in png_do_scale_16_to_8");
-
-   if (row_info->bit_depth == 16)
-   {
-      png_bytep sp = row; /* source */
-      png_bytep dp = row; /* destination */
-      png_bytep ep = sp + row_info->rowbytes; /* end+1 */
-
-      while (sp < ep)
-      {
-         /* The input is an array of 16 bit components, these must be scaled to
-          * 8 bits each.  For a 16 bit value V the required value (from the PNG
-          * specification) is:
-          *
-          *    (V * 255) / 65535
-          *
-          * This reduces to round(V / 257), or floor((V + 128.5)/257)
-          *
-          * Represent V as the two byte value vhi.vlo.  Make a guess that the
-          * result is the top byte of V, vhi, then the correction to this value
-          * is:
-          *
-          *    error = floor(((V-vhi.vhi) + 128.5) / 257)
-          *          = floor(((vlo-vhi) + 128.5) / 257)
-          *
-          * This can be approximated using integer arithmetic (and a signed
-          * shift):
-          *
-          *    error = (vlo-vhi+128) >> 8;
-          *
-          * The approximate differs from the exact answer only when (vlo-vhi) is
-          * 128; it then gives a correction of +1 when the exact correction is
-          * 0.  This gives 128 errors.  The exact answer (correct for all 16 bit
-          * input values) is:
-          *
-          *    error = (vlo-vhi+128)*65535 >> 24;
-          *
-          * An alternative arithmetic calculation which also gives no errors is:
-          *
-          *    (V * 255 + 32895) >> 16
-          */
-
-         png_int_32 tmp = *sp++; /* must be signed! */
-         tmp += (((int)*sp++ - tmp + 128) * 65535) >> 24;
-         *dp++ = (png_byte)tmp;
-      }
-
-      row_info->bit_depth = 8;
-      row_info->pixel_depth = (png_byte)(8 * row_info->channels);
-      row_info->rowbytes = row_info->width * row_info->channels;
-   }
-}
-#endif
-
-#ifdef PNG_READ_STRIP_16_TO_8_SUPPORTED
-void /* PRIVATE */
-/* Simply discard the low byte.  This was the default behavior prior
- * to libpng-1.5.4.
- */
 png_do_chop(png_row_infop row_info, png_bytep row)
 {
    png_debug(1, "in png_do_chop");
 
+#ifdef PNG_USELESS_TESTS_SUPPORTED
+   if (row != NULL && row_info != NULL && row_info->bit_depth == 16)
+#else
    if (row_info->bit_depth == 16)
+#endif
    {
-      png_bytep sp = row; /* source */
-      png_bytep dp = row; /* destination */
-      png_bytep ep = sp + row_info->rowbytes; /* end+1 */
+      png_bytep sp = row;
+      png_bytep dp = row;
+      png_uint_32 i;
+      png_uint_32 istop = row_info->width * row_info->channels;
 
-      while (sp < ep)
+      for (i = 0; i<istop; i++, sp += 2, dp++)
       {
-         *dp++ = *sp;
-         sp += 2; /* skip low byte */
+#ifdef PNG_READ_16_TO_8_ACCURATE_SCALE_SUPPORTED
+      /* This does a more accurate scaling of the 16-bit color
+       * value, rather than a simple low-byte truncation.
+       *
+       * What the ideal calculation should be:
+       *   *dp = (((((png_uint_32)(*sp) << 8) |
+       *          (png_uint_32)(*(sp + 1))) * 255 + 127)
+       *          / (png_uint_32)65535L;
+       *
+       * GRR: no, I think this is what it really should be:
+       *   *dp = (((((png_uint_32)(*sp) << 8) |
+       *           (png_uint_32)(*(sp + 1))) + 128L)
+       *           / (png_uint_32)257L;
+       *
+       * GRR: here's the exact calculation with shifts:
+       *   temp = (((png_uint_32)(*sp) << 8) |
+       *           (png_uint_32)(*(sp + 1))) + 128L;
+       *   *dp = (temp - (temp >> 8)) >> 8;
+       *
+       * Approximate calculation with shift/add instead of multiply/divide:
+       *   *dp = ((((png_uint_32)(*sp) << 8) |
+       *          (png_uint_32)((int)(*(sp + 1)) - *sp)) + 128) >> 8;
+       *
+       * What we actually do to avoid extra shifting and conversion:
+       */
+
+         *dp = *sp + ((((int)(*(sp + 1)) - *sp) > 128) ? 1 : 0);
+#else
+       /* Simply discard the low order byte */
+         *dp = *sp;
+#endif
       }
-
       row_info->bit_depth = 8;
       row_info->pixel_depth = (png_byte)(8 * row_info->channels);
       row_info->rowbytes = row_info->width * row_info->channels;
    }
 }
 #endif
 
 #ifdef PNG_READ_SWAP_ALPHA_SUPPORTED
 void /* PRIVATE */
 png_do_read_swap_alpha(png_row_infop row_info, png_bytep row)
 {
    png_debug(1, "in png_do_read_swap_alpha");
 
+#ifdef PNG_USELESS_TESTS_SUPPORTED
+   if (row != NULL && row_info != NULL)
+#endif
    {
       png_uint_32 row_width = row_info->width;
       if (row_info->color_type == PNG_COLOR_TYPE_RGB_ALPHA)
       {
          /* This converts from RGBA to ARGB */
          if (row_info->bit_depth == 8)
          {
             png_bytep sp = row + row_info->rowbytes;
             png_bytep dp = sp;
             png_byte save;
             png_uint_32 i;
 
             for (i = 0; i < row_width; i++)
             {
                save = *(--sp);
                *(--dp) = *(--sp);
                *(--dp) = *(--sp);
                *(--dp) = *(--sp);
                *(--dp) = save;
             }
          }
-
-#ifdef PNG_READ_16BIT_SUPPORTED
          /* This converts from RRGGBBAA to AARRGGBB */
          else
          {
             png_bytep sp = row + row_info->rowbytes;
             png_bytep dp = sp;
             png_byte save[2];
             png_uint_32 i;
 
             for (i = 0; i < row_width; i++)
             {
                save[0] = *(--sp);
                save[1] = *(--sp);
                *(--dp) = *(--sp);
                *(--dp) = *(--sp);
                *(--dp) = *(--sp);
                *(--dp) = *(--sp);
                *(--dp) = *(--sp);
                *(--dp) = *(--sp);
                *(--dp) = save[0];
                *(--dp) = save[1];
             }
          }
-#endif
       }
-
       else if (row_info->color_type == PNG_COLOR_TYPE_GRAY_ALPHA)
       {
          /* This converts from GA to AG */
          if (row_info->bit_depth == 8)
          {
             png_bytep sp = row + row_info->rowbytes;
             png_bytep dp = sp;
             png_byte save;
             png_uint_32 i;
 
             for (i = 0; i < row_width; i++)
             {
                save = *(--sp);
                *(--dp) = *(--sp);
                *(--dp) = save;
             }
          }
-
-#ifdef PNG_READ_16BIT_SUPPORTED
          /* This converts from GGAA to AAGG */
          else
          {
             png_bytep sp = row + row_info->rowbytes;
             png_bytep dp = sp;
             png_byte save[2];
             png_uint_32 i;
 
             for (i = 0; i < row_width; i++)
             {
                save[0] = *(--sp);
                save[1] = *(--sp);
                *(--dp) = *(--sp);
                *(--dp) = *(--sp);
                *(--dp) = save[0];
                *(--dp) = save[1];
             }
          }
-#endif
       }
    }
 }
 #endif
 
 #ifdef PNG_READ_INVERT_ALPHA_SUPPORTED
 void /* PRIVATE */
 png_do_read_invert_alpha(png_row_infop row_info, png_bytep row)
 {
-   png_uint_32 row_width;
    png_debug(1, "in png_do_read_invert_alpha");
 
-   row_width = row_info->width;
-   if (row_info->color_type == PNG_COLOR_TYPE_RGB_ALPHA)
+#ifdef PNG_USELESS_TESTS_SUPPORTED
+   if (row != NULL && row_info != NULL)
+#endif
    {
-      if (row_info->bit_depth == 8)
+      png_uint_32 row_width = row_info->width;
+      if (row_info->color_type == PNG_COLOR_TYPE_RGB_ALPHA)
       {
          /* This inverts the alpha channel in RGBA */
-         png_bytep sp = row + row_info->rowbytes;
-         png_bytep dp = sp;
-         png_uint_32 i;
+         if (row_info->bit_depth == 8)
+         {
+            png_bytep sp = row + row_info->rowbytes;
+            png_bytep dp = sp;
+            png_uint_32 i;
 
-         for (i = 0; i < row_width; i++)
+            for (i = 0; i < row_width; i++)
+            {
+               *(--dp) = (png_byte)(255 - *(--sp));
+
+/*             This does nothing:
+               *(--dp) = *(--sp);
+               *(--dp) = *(--sp);
+               *(--dp) = *(--sp);
+               We can replace it with:
+*/
+               sp-=3;
+               dp=sp;
+            }
+         }
+         /* This inverts the alpha channel in RRGGBBAA */
+         else
          {
-            *(--dp) = (png_byte)(255 - *(--sp));
+            png_bytep sp = row + row_info->rowbytes;
+            png_bytep dp = sp;
+            png_uint_32 i;
 
-/*          This does nothing:
-            *(--dp) = *(--sp);
-            *(--dp) = *(--sp);
-            *(--dp) = *(--sp);
-            We can replace it with:
+            for (i = 0; i < row_width; i++)
+            {
+               *(--dp) = (png_byte)(255 - *(--sp));
+               *(--dp) = (png_byte)(255 - *(--sp));
+
+/*             This does nothing:
+               *(--dp) = *(--sp);
+               *(--dp) = *(--sp);
+               *(--dp) = *(--sp);
+               *(--dp) = *(--sp);
+               *(--dp) = *(--sp);
+               *(--dp) = *(--sp);
+               We can replace it with:
 */
-            sp-=3;
-            dp=sp;
+               sp-=6;
+               dp=sp;
+            }
          }
       }
+      else if (row_info->color_type == PNG_COLOR_TYPE_GRAY_ALPHA)
+      {
+         /* This inverts the alpha channel in GA */
+         if (row_info->bit_depth == 8)
+         {
+            png_bytep sp = row + row_info->rowbytes;
+            png_bytep dp = sp;
+            png_uint_32 i;
 
-#ifdef PNG_READ_16BIT_SUPPORTED
-      /* This inverts the alpha channel in RRGGBBAA */
-      else
-      {
-         png_bytep sp = row + row_info->rowbytes;
-         png_bytep dp = sp;
-         png_uint_32 i;
+            for (i = 0; i < row_width; i++)
+            {
+               *(--dp) = (png_byte)(255 - *(--sp));
+               *(--dp) = *(--sp);
+            }
+         }
+         /* This inverts the alpha channel in GGAA */
+         else
+         {
+            png_bytep sp  = row + row_info->rowbytes;
+            png_bytep dp = sp;
+            png_uint_32 i;
 
-         for (i = 0; i < row_width; i++)
-         {
-            *(--dp) = (png_byte)(255 - *(--sp));
-            *(--dp) = (png_byte)(255 - *(--sp));
-
-/*          This does nothing:
-            *(--dp) = *(--sp);
-            *(--dp) = *(--sp);
-            *(--dp) = *(--sp);
-            *(--dp) = *(--sp);
-            *(--dp) = *(--sp);
-            *(--dp) = *(--sp);
-            We can replace it with:
+            for (i = 0; i < row_width; i++)
+            {
+               *(--dp) = (png_byte)(255 - *(--sp));
+               *(--dp) = (png_byte)(255 - *(--sp));
+/*
+               *(--dp) = *(--sp);
+               *(--dp) = *(--sp);
 */
-            sp-=6;
-            dp=sp;
+               sp-=2;
+               dp=sp;
+            }
          }
       }
-#endif
-   }
-   else if (row_info->color_type == PNG_COLOR_TYPE_GRAY_ALPHA)
-   {
-      if (row_info->bit_depth == 8)
-      {
-         /* This inverts the alpha channel in GA */
-         png_bytep sp = row + row_info->rowbytes;
-         png_bytep dp = sp;
-         png_uint_32 i;
-
-         for (i = 0; i < row_width; i++)
-         {
-            *(--dp) = (png_byte)(255 - *(--sp));
-            *(--dp) = *(--sp);
-         }
-      }
-
-#ifdef PNG_READ_16BIT_SUPPORTED
-      else
-      {
-         /* This inverts the alpha channel in GGAA */
-         png_bytep sp  = row + row_info->rowbytes;
-         png_bytep dp = sp;
-         png_uint_32 i;
-
-         for (i = 0; i < row_width; i++)
-         {
-            *(--dp) = (png_byte)(255 - *(--sp));
-            *(--dp) = (png_byte)(255 - *(--sp));
-/*
-            *(--dp) = *(--sp);
-            *(--dp) = *(--sp);
-*/
-            sp-=2;
-            dp=sp;
-         }
-      }
-#endif
    }
 }
 #endif
 
 #ifdef PNG_READ_FILLER_SUPPORTED
 /* Add filler channel if we have RGB color */
 void /* PRIVATE */
 png_do_read_filler(png_row_infop row_info, png_bytep row,
-    png_uint_32 filler, png_uint_32 flags)
+   png_uint_32 filler, png_uint_32 flags)
 {
    png_uint_32 i;
    png_uint_32 row_width = row_info->width;
 
-#ifdef PNG_READ_16BIT_SUPPORTED
    png_byte hi_filler = (png_byte)((filler>>8) & 0xff);
-#endif
    png_byte lo_filler = (png_byte)(filler & 0xff);
 
    png_debug(1, "in png_do_read_filler");
 
    if (
+#ifdef PNG_USELESS_TESTS_SUPPORTED
+       row != NULL  && row_info != NULL &&
+#endif
        row_info->color_type == PNG_COLOR_TYPE_GRAY)
    {
       if (row_info->bit_depth == 8)
       {
+         /* This changes the data from G to GX */
          if (flags & PNG_FLAG_FILLER_AFTER)
          {
-            /* This changes the data from G to GX */
             png_bytep sp = row + (png_size_t)row_width;
             png_bytep dp =  sp + (png_size_t)row_width;
             for (i = 1; i < row_width; i++)
             {
                *(--dp) = lo_filler;
                *(--dp) = *(--sp);
             }
             *(--dp) = lo_filler;
             row_info->channels = 2;
             row_info->pixel_depth = 16;
             row_info->rowbytes = row_width * 2;
          }
-
+      /* This changes the data from G to XG */
          else
          {
-            /* This changes the data from G to XG */
             png_bytep sp = row + (png_size_t)row_width;
             png_bytep dp = sp  + (png_size_t)row_width;
             for (i = 0; i < row_width; i++)
             {
                *(--dp) = *(--sp);
                *(--dp) = lo_filler;
             }
             row_info->channels = 2;
             row_info->pixel_depth = 16;
             row_info->rowbytes = row_width * 2;
          }
       }
-
-#ifdef PNG_READ_16BIT_SUPPORTED
       else if (row_info->bit_depth == 16)
       {
+         /* This changes the data from GG to GGXX */
          if (flags & PNG_FLAG_FILLER_AFTER)
          {
-            /* This changes the data from GG to GGXX */
             png_bytep sp = row + (png_size_t)row_width * 2;
             png_bytep dp = sp  + (png_size_t)row_width * 2;
             for (i = 1; i < row_width; i++)
             {
                *(--dp) = hi_filler;
                *(--dp) = lo_filler;
                *(--dp) = *(--sp);
                *(--dp) = *(--sp);
             }
             *(--dp) = hi_filler;
             *(--dp) = lo_filler;
             row_info->channels = 2;
             row_info->pixel_depth = 32;
             row_info->rowbytes = row_width * 4;
          }
-
+         /* This changes the data from GG to XXGG */
          else
          {
-            /* This changes the data from GG to XXGG */
             png_bytep sp = row + (png_size_t)row_width * 2;
             png_bytep dp = sp  + (png_size_t)row_width * 2;
             for (i = 0; i < row_width; i++)
             {
                *(--dp) = *(--sp);
                *(--dp) = *(--sp);
                *(--dp) = hi_filler;
                *(--dp) = lo_filler;
             }
             row_info->channels = 2;
             row_info->pixel_depth = 32;
             row_info->rowbytes = row_width * 4;
          }
       }
-#endif
    } /* COLOR_TYPE == GRAY */
    else if (row_info->color_type == PNG_COLOR_TYPE_RGB)
    {
       if (row_info->bit_depth == 8)
       {
+         /* This changes the data from RGB to RGBX */
          if (flags & PNG_FLAG_FILLER_AFTER)
          {
-            /* This changes the data from RGB to RGBX */
             png_bytep sp = row + (png_size_t)row_width * 3;
             png_bytep dp = sp  + (png_size_t)row_width;
             for (i = 1; i < row_width; i++)
             {
                *(--dp) = lo_filler;
                *(--dp) = *(--sp);
                *(--dp) = *(--sp);
                *(--dp) = *(--sp);
             }
             *(--dp) = lo_filler;
             row_info->channels = 4;
             row_info->pixel_depth = 32;
             row_info->rowbytes = row_width * 4;
          }
-
+      /* This changes the data from RGB to XRGB */
          else
          {
-            /* This changes the data from RGB to XRGB */
             png_bytep sp = row + (png_size_t)row_width * 3;
             png_bytep dp = sp + (png_size_t)row_width;
             for (i = 0; i < row_width; i++)
             {
                *(--dp) = *(--sp);
                *(--dp) = *(--sp);
                *(--dp) = *(--sp);
                *(--dp) = lo_filler;
             }
             row_info->channels = 4;
             row_info->pixel_depth = 32;
             row_info->rowbytes = row_width * 4;
          }
       }
-
-#ifdef PNG_READ_16BIT_SUPPORTED
       else if (row_info->bit_depth == 16)
       {
+         /* This changes the data from RRGGBB to RRGGBBXX */
          if (flags & PNG_FLAG_FILLER_AFTER)
          {
-            /* This changes the data from RRGGBB to RRGGBBXX */
             png_bytep sp = row + (png_size_t)row_width * 6;
             png_bytep dp = sp  + (png_size_t)row_width * 2;
             for (i = 1; i < row_width; i++)
             {
                *(--dp) = hi_filler;
                *(--dp) = lo_filler;
                *(--dp) = *(--sp);
                *(--dp) = *(--sp);
                *(--dp) = *(--sp);
                *(--dp) = *(--sp);
                *(--dp) = *(--sp);
                *(--dp) = *(--sp);
             }
             *(--dp) = hi_filler;
             *(--dp) = lo_filler;
             row_info->channels = 4;
             row_info->pixel_depth = 64;
             row_info->rowbytes = row_width * 8;
          }
-
+         /* This changes the data from RRGGBB to XXRRGGBB */
          else
          {
-            /* This changes the data from RRGGBB to XXRRGGBB */
             png_bytep sp = row + (png_size_t)row_width * 6;
             png_bytep dp = sp  + (png_size_t)row_width * 2;
             for (i = 0; i < row_width; i++)
             {
                *(--dp) = *(--sp);
                *(--dp) = *(--sp);
                *(--dp) = *(--sp);
                *(--dp) = *(--sp);
                *(--dp) = *(--sp);
                *(--dp) = *(--sp);
                *(--dp) = hi_filler;
                *(--dp) = lo_filler;
             }
-
             row_info->channels = 4;
             row_info->pixel_depth = 64;
             row_info->rowbytes = row_width * 8;
          }
       }
-#endif
    } /* COLOR_TYPE == RGB */
 }
 #endif
 
 #ifdef PNG_READ_GRAY_TO_RGB_SUPPORTED
 /* Expand grayscale files to RGB, with or without alpha */
 void /* PRIVATE */
 png_do_gray_to_rgb(png_row_infop row_info, png_bytep row)
 {
    png_uint_32 i;
    png_uint_32 row_width = row_info->width;
 
    png_debug(1, "in png_do_gray_to_rgb");
 
    if (row_info->bit_depth >= 8 &&
-       !(row_info->color_type & PNG_COLOR_MASK_COLOR))
+#ifdef PNG_USELESS_TESTS_SUPPORTED
+       row != NULL && row_info != NULL &&
+#endif
+      !(row_info->color_type & PNG_COLOR_MASK_COLOR))
    {
       if (row_info->color_type == PNG_COLOR_TYPE_GRAY)
       {
          if (row_info->bit_depth == 8)
          {
-            /* This changes G to RGB */
             png_bytep sp = row + (png_size_t)row_width - 1;
             png_bytep dp = sp  + (png_size_t)row_width * 2;
             for (i = 0; i < row_width; i++)
             {
                *(dp--) = *sp;
                *(dp--) = *sp;
                *(dp--) = *(sp--);
             }
          }
-
          else
          {
-            /* This changes GG to RRGGBB */
             png_bytep sp = row + (png_size_t)row_width * 2 - 1;
             png_bytep dp = sp  + (png_size_t)row_width * 4;
             for (i = 0; i < row_width; i++)
             {
                *(dp--) = *sp;
                *(dp--) = *(sp - 1);
                *(dp--) = *sp;
                *(dp--) = *(sp - 1);
                *(dp--) = *(sp--);
                *(dp--) = *(sp--);
             }
          }
       }
-
       else if (row_info->color_type == PNG_COLOR_TYPE_GRAY_ALPHA)
       {
          if (row_info->bit_depth == 8)
          {
-            /* This changes GA to RGBA */
             png_bytep sp = row + (png_size_t)row_width * 2 - 1;
             png_bytep dp = sp  + (png_size_t)row_width * 2;
             for (i = 0; i < row_width; i++)
             {
                *(dp--) = *(sp--);
                *(dp--) = *sp;
                *(dp--) = *sp;
                *(dp--) = *(sp--);
             }
          }
-
          else
          {
-            /* This changes GGAA to RRGGBBAA */
             png_bytep sp = row + (png_size_t)row_width * 4 - 1;
             png_bytep dp = sp  + (png_size_t)row_width * 4;
             for (i = 0; i < row_width; i++)
             {
                *(dp--) = *(sp--);
                *(dp--) = *(sp--);
                *(dp--) = *sp;
                *(dp--) = *(sp - 1);
                *(dp--) = *sp;
                *(dp--) = *(sp - 1);
                *(dp--) = *(sp--);
                *(dp--) = *(sp--);
             }
          }
       }
-      row_info->channels = (png_byte)(row_info->channels + 2);
+      row_info->channels += (png_byte)2;
       row_info->color_type |= PNG_COLOR_MASK_COLOR;
       row_info->pixel_depth = (png_byte)(row_info->channels *
-          row_info->bit_depth);
+         row_info->bit_depth);
       row_info->rowbytes = PNG_ROWBYTES(row_info->pixel_depth, row_width);
    }
 }
 #endif
 
 #ifdef PNG_READ_RGB_TO_GRAY_SUPPORTED
 /* Reduce RGB files to grayscale, with or without alpha
- * using the equation given in Poynton's ColorFAQ of 1998-01-04 at
- * <http://www.inforamp.net/~poynton/>  (THIS LINK IS DEAD June 2008 but
- * versions dated 1998 through November 2002 have been archived at
- * http://web.archive.org/web/20000816232553/http://www.inforamp.net/
- * ~poynton/notes/colour_and_gamma/ColorFAQ.txt )
+ * using the equation given in Poynton's ColorFAQ at
+ * <http://www.inforamp.net/~poynton/>  (THIS LINK IS DEAD June 2008)
+ * New link:
+ * <http://www.poynton.com/notes/colour_and_gamma/>
  * Charles Poynton poynton at poynton.com
  *
  *     Y = 0.212671 * R + 0.715160 * G + 0.072169 * B
  *
+ *  We approximate this with
+ *
+ *     Y = 0.21268 * R    + 0.7151 * G    + 0.07217 * B
+ *
  *  which can be expressed with integers as
  *
  *     Y = (6969 * R + 23434 * G + 2365 * B)/32768
  *
- * Poynton's current link (as of January 2003 through July 2011):
- * <http://www.poynton.com/notes/colour_and_gamma/>
- * has changed the numbers slightly:
- *
- *     Y = 0.2126*R + 0.7152*G + 0.0722*B
- *
- *  which can be expressed with integers as
- *
- *     Y = (6966 * R + 23436 * G + 2366 * B)/32768
- *
- *  Historically, however, libpng uses numbers derived from the ITU-R Rec 709
- *  end point chromaticities and the D65 white point.  Depending on the
- *  precision used for the D65 white point this produces a variety of different
- *  numbers, however if the four decimal place value used in ITU-R Rec 709 is
- *  used (0.3127,0.3290) the Y calculation would be:
- *
- *     Y = (6968 * R + 23435 * G + 2366 * B)/32768
- *
- *  While this is correct the rounding results in an overflow for white, because
- *  the sum of the rounded coefficients is 32769, not 32768.  Consequently
- *  libpng uses, instead, the closest non-overflowing approximation:
- *
- *     Y = (6968 * R + 23434 * G + 2366 * B)/32768
- *
- *  Starting with libpng-1.5.5, if the image being converted has a cHRM chunk
- *  (including an sRGB chunk) then the chromaticities are used to calculate the
- *  coefficients.  See the chunk handling in pngrutil.c for more information.
- *
- *  In all cases the calculation is to be done in a linear colorspace.  If no
- *  gamma information is available to correct the encoding of the original RGB
- *  values this results in an implicit assumption that the original PNG RGB
- *  values were linear.
- *
- *  Other integer coefficents can be used via png_set_rgb_to_gray().  Because
- *  the API takes just red and green coefficients the blue coefficient is
- *  calculated to make the sum 32768.  This will result in different rounding
- *  to that used above.
+ *  The calculation is to be done in a linear colorspace.
+ *
+ *  Other integer coefficents can be used via png_set_rgb_to_gray().
  */
 int /* PRIVATE */
-png_do_rgb_to_gray(png_structrp png_ptr, png_row_infop row_info, png_bytep row)
+png_do_rgb_to_gray(png_structp png_ptr, png_row_infop row_info, png_bytep row)
 
 {
+   png_uint_32 i;
+
+   png_uint_32 row_width = row_info->width;
    int rgb_error = 0;
 
    png_debug(1, "in png_do_rgb_to_gray");
 
-   if (!(row_info->color_type & PNG_COLOR_MASK_PALETTE) &&
-       (row_info->color_type & PNG_COLOR_MASK_COLOR))
+   if (
+#ifdef PNG_USELESS_TESTS_SUPPORTED
+       row != NULL && row_info != NULL &&
+#endif
+      (row_info->color_type & PNG_COLOR_MASK_COLOR))
    {
-      PNG_CONST png_uint_32 rc = png_ptr->rgb_to_gray_red_coeff;
-      PNG_CONST png_uint_32 gc = png_ptr->rgb_to_gray_green_coeff;
-      PNG_CONST png_uint_32 bc = 32768 - rc - gc;
-      PNG_CONST png_uint_32 row_width = row_info->width;
-      PNG_CONST int have_alpha =
-         (row_info->color_type & PNG_COLOR_MASK_ALPHA) != 0;
-
-      if (row_info->bit_depth == 8)
+      png_uint_32 rc = png_ptr->rgb_to_gray_red_coeff;
+      png_uint_32 gc = png_ptr->rgb_to_gray_green_coeff;
+      png_uint_32 bc = png_ptr->rgb_to_gray_blue_coeff;
+
+      if (row_info->color_type == PNG_COLOR_TYPE_RGB)
       {
-#ifdef PNG_READ_GAMMA_SUPPORTED
-         /* Notice that gamma to/from 1 are not necessarily inverses (if
-          * there is an overall gamma correction).  Prior to 1.5.5 this code
-          * checked the linearized values for equality; this doesn't match
-          * the documentation, the original values must be checked.
-          */
-         if (png_ptr->gamma_from_1 != NULL && png_ptr->gamma_to_1 != NULL)
-         {
-            png_bytep sp = row;
-            png_bytep dp = row;
-            png_uint_32 i;
-
-            for (i = 0; i < row_width; i++)
-            {
-               png_byte red   = *(sp++);
-               png_byte green = *(sp++);
-               png_byte blue  = *(sp++);
-
-               if (red != green || red != blue)
-               {
-                  red = png_ptr->gamma_to_1[red];
-                  green = png_ptr->gamma_to_1[green];
-                  blue = png_ptr->gamma_to_1[blue];
-
-                  rgb_error |= 1;
-                  *(dp++) = png_ptr->gamma_from_1[
-                      (rc*red + gc*green + bc*blue + 16384)>>15];
-               }
-
-               else
-               {
-                  /* If there is no overall correction the table will not be
-                   * set.
-                   */
-                  if (png_ptr->gamma_table != NULL)
-                     red = png_ptr->gamma_table[red];
-
-                  *(dp++) = red;
-               }
-
-               if (have_alpha)
+         if (row_info->bit_depth == 8)
+         {
+#if defined(PNG_READ_GAMMA_SUPPORTED) || defined(PNG_READ_BACKGROUND_SUPPORTED)
+            if (png_ptr->gamma_from_1 != NULL && png_ptr->gamma_to_1 != NULL)
+            {
+               png_bytep sp = row;
+               png_bytep dp = row;
+
+               for (i = 0; i < row_width; i++)
+               {
+                  png_byte red   = png_ptr->gamma_to_1[*(sp++)];
+                  png_byte green = png_ptr->gamma_to_1[*(sp++)];
+                  png_byte blue  = png_ptr->gamma_to_1[*(sp++)];
+                  if (red != green || red != blue)
+                  {
+                     rgb_error |= 1;
+                     *(dp++) = png_ptr->gamma_from_1[
+                       (rc*red + gc*green + bc*blue)>>15];
+                  }
+                  else
+                     *(dp++) = *(sp - 1);
+               }
+            }
+            else
+#endif
+            {
+               png_bytep sp = row;
+               png_bytep dp = row;
+               for (i = 0; i < row_width; i++)
+               {
+                  png_byte red   = *(sp++);
+                  png_byte green = *(sp++);
+                  png_byte blue  = *(sp++);
+                  if (red != green || red != blue)
+                  {
+                     rgb_error |= 1;
+                     *(dp++) = (png_byte)((rc*red + gc*green + bc*blue)>>15);
+                  }
+                  else
+                     *(dp++) = *(sp - 1);
+               }
+            }
+         }
+
+         else /* RGB bit_depth == 16 */
+         {
+#if defined(PNG_READ_GAMMA_SUPPORTED) || defined(PNG_READ_BACKGROUND_SUPPORTED)
+            if (png_ptr->gamma_16_to_1 != NULL &&
+                png_ptr->gamma_16_from_1 != NULL)
+            {
+               png_bytep sp = row;
+               png_bytep dp = row;
+               for (i = 0; i < row_width; i++)
+               {
+                  png_uint_16 red, green, blue, w;
+
+                  red   = (png_uint_16)(((*(sp))<<8) | *(sp+1)); sp+=2;
+                  green = (png_uint_16)(((*(sp))<<8) | *(sp+1)); sp+=2;
+                  blue  = (png_uint_16)(((*(sp))<<8) | *(sp+1)); sp+=2;
+
+                  if (red == green && red == blue)
+                     w = red;
+                  else
+                  {
+                     png_uint_16 red_1   = png_ptr->gamma_16_to_1[(red&0xff) >>
+                                  png_ptr->gamma_shift][red>>8];
+                     png_uint_16 green_1 =
+                         png_ptr->gamma_16_to_1[(green&0xff) >>
+                                  png_ptr->gamma_shift][green>>8];
+                     png_uint_16 blue_1  = png_ptr->gamma_16_to_1[(blue&0xff) >>
+                                  png_ptr->gamma_shift][blue>>8];
+                     png_uint_16 gray16  = (png_uint_16)((rc*red_1 + gc*green_1
+                                  + bc*blue_1)>>15);
+                     w = png_ptr->gamma_16_from_1[(gray16&0xff) >>
+                         png_ptr->gamma_shift][gray16 >> 8];
+                     rgb_error |= 1;
+                  }
+
+                  *(dp++) = (png_byte)((w>>8) & 0xff);
+                  *(dp++) = (png_byte)(w & 0xff);
+               }
+            }
+            else
+#endif
+            {
+               png_bytep sp = row;
+               png_bytep dp = row;
+               for (i = 0; i < row_width; i++)
+               {
+                  png_uint_16 red, green, blue, gray16;
+
+                  red   = (png_uint_16)(((*(sp))<<8) | *(sp+1)); sp+=2;
+                  green = (png_uint_16)(((*(sp))<<8) | *(sp+1)); sp+=2;
+                  blue  = (png_uint_16)(((*(sp))<<8) | *(sp+1)); sp+=2;
+
+                  if (red != green || red != blue)
+                     rgb_error |= 1;
+                  gray16  = (png_uint_16)((rc*red + gc*green + bc*blue)>>15);
+                  *(dp++) = (png_byte)((gray16>>8) & 0xff);
+                  *(dp++) = (png_byte)(gray16 & 0xff);
+               }
+            }
+         }
+      }
+      if (row_info->color_type == PNG_COLOR_TYPE_RGB_ALPHA)
+      {
+         if (row_info->bit_depth == 8)
+         {
+#if defined(PNG_READ_GAMMA_SUPPORTED) || defined(PNG_READ_BACKGROUND_SUPPORTED)
+            if (png_ptr->gamma_from_1 != NULL && png_ptr->gamma_to_1 != NULL)
+            {
+               png_bytep sp = row;
+               png_bytep dp = row;
+               for (i = 0; i < row_width; i++)
+               {
+                  png_byte red   = png_ptr->gamma_to_1[*(sp++)];
+                  png_byte green = png_ptr->gamma_to_1[*(sp++)];
+                  png_byte blue  = png_ptr->gamma_to_1[*(sp++)];
+                  if (red != green || red != blue)
+                     rgb_error |= 1;
+                  *(dp++) =  png_ptr->gamma_from_1
+                             [(rc*red + gc*green + bc*blue)>>15];
+                  *(dp++) = *(sp++);  /* alpha */
+               }
+            }
+            else
+#endif
+            {
+               png_bytep sp = row;
+               png_bytep dp = row;
+               for (i = 0; i < row_width; i++)
+               {
+                  png_byte red   = *(sp++);
+                  png_byte green = *(sp++);
+                  png_byte blue  = *(sp++);
+                  if (red != green || red != blue)
+                     rgb_error |= 1;
+                  *(dp++) =  (png_byte)((rc*red + gc*green + bc*blue)>>15);
+                  *(dp++) = *(sp++);  /* alpha */
+               }
+            }
+         }
+         else /* RGBA bit_depth == 16 */
+         {
+#if defined(PNG_READ_GAMMA_SUPPORTED) || defined(PNG_READ_BACKGROUND_SUPPORTED)
+            if (png_ptr->gamma_16_to_1 != NULL &&
+                png_ptr->gamma_16_from_1 != NULL)
+            {
+               png_bytep sp = row;
+               png_bytep dp = row;
+               for (i = 0; i < row_width; i++)
+               {
+                  png_uint_16 red, green, blue, w;
+
+                  red   = (png_uint_16)(((*(sp))<<8) | *(sp+1)); sp+=2;
+                  green = (png_uint_16)(((*(sp))<<8) | *(sp+1)); sp+=2;
+                  blue  = (png_uint_16)(((*(sp))<<8) | *(sp+1)); sp+=2;
+
+                  if (red == green && red == blue)
+                     w = red;
+                  else
+                  {
+                     png_uint_16 red_1   = png_ptr->gamma_16_to_1[(red&0xff) >>
+                         png_ptr->gamma_shift][red>>8];
+                     png_uint_16 green_1 =
+                         png_ptr->gamma_16_to_1[(green&0xff) >>
+                         png_ptr->gamma_shift][green>>8];
+                     png_uint_16 blue_1  = png_ptr->gamma_16_to_1[(blue&0xff) >>
+                         png_ptr->gamma_shift][blue>>8];
+                     png_uint_16 gray16  = (png_uint_16)((rc * red_1
+                         + gc * green_1 + bc * blue_1)>>15);
+                     w = png_ptr->gamma_16_from_1[(gray16&0xff) >>
+                         png_ptr->gamma_shift][gray16 >> 8];
+                     rgb_error |= 1;
+                  }
+
+                  *(dp++) = (png_byte)((w>>8) & 0xff);
+                  *(dp++) = (png_byte)(w & 0xff);
+                  *(dp++) = *(sp++);  /* alpha */
                   *(dp++) = *(sp++);
-            }
-         }
-         else
-#endif
-         {
-            png_bytep sp = row;
-            png_bytep dp = row;
-            png_uint_32 i;
-
-            for (i = 0; i < row_width; i++)
-            {
-               png_byte red   = *(sp++);
-               png_byte green = *(sp++);
-               png_byte blue  = *(sp++);
-
-               if (red != green || red != blue)
-               {
-                  rgb_error |= 1;
-                  /* NOTE: this is the historical approach which simply
-                   * truncates the results.
-                   */
-                  *(dp++) = (png_byte)((rc*red + gc*green + bc*blue)>>15);
-               }
-
-               else
-                  *(dp++) = red;
-
-               if (have_alpha)
+               }
+            }
+            else
+#endif
+            {
+               png_bytep sp = row;
+               png_bytep dp = row;
+               for (i = 0; i < row_width; i++)
+               {
+                  png_uint_16 red, green, blue, gray16;
+                  red   = (png_uint_16)((*(sp)<<8) | *(sp+1)); sp+=2;
+                  green = (png_uint_16)((*(sp)<<8) | *(sp+1)); sp+=2;
+                  blue  = (png_uint_16)((*(sp)<<8) | *(sp+1)); sp+=2;
+                  if (red != green || red != blue)
+                     rgb_error |= 1;
+                  gray16  = (png_uint_16)((rc*red + gc*green + bc*blue)>>15);
+                  *(dp++) = (png_byte)((gray16>>8) & 0xff);
+                  *(dp++) = (png_byte)(gray16 & 0xff);
+                  *(dp++) = *(sp++);  /* alpha */
                   *(dp++) = *(sp++);
+               }
             }
          }
       }
-
-      else /* RGB bit_depth == 16 */
-      {
-#ifdef PNG_READ_GAMMA_SUPPORTED
-         if (png_ptr->gamma_16_to_1 != NULL && png_ptr->gamma_16_from_1 != NULL)
-         {
-            png_bytep sp = row;
-            png_bytep dp = row;
-            png_uint_32 i;
-
-            for (i = 0; i < row_width; i++)
-            {
-               png_uint_16 red, green, blue, w;
-
-               red   = (png_uint_16)(((*(sp))<<8) | *(sp + 1)); sp += 2;
-               green = (png_uint_16)(((*(sp))<<8) | *(sp + 1)); sp += 2;
-               blue  = (png_uint_16)(((*(sp))<<8) | *(sp + 1)); sp += 2;
-
-               if (red == green && red == blue)
-               {
-                  if (png_ptr->gamma_16_table != NULL)
-                     w = png_ptr->gamma_16_table[(red&0xff)
-                         >> png_ptr->gamma_shift][red>>8];
-
-                  else
-                     w = red;
-               }
-
-               else
-               {
-                  png_uint_16 red_1   = png_ptr->gamma_16_to_1[(red&0xff)
-                      >> png_ptr->gamma_shift][red>>8];
-                  png_uint_16 green_1 =
-                      png_ptr->gamma_16_to_1[(green&0xff) >>
-                      png_ptr->gamma_shift][green>>8];
-                  png_uint_16 blue_1  = png_ptr->gamma_16_to_1[(blue&0xff)
-                      >> png_ptr->gamma_shift][blue>>8];
-                  png_uint_16 gray16  = (png_uint_16)((rc*red_1 + gc*green_1
-                      + bc*blue_1 + 16384)>>15);
-                  w = png_ptr->gamma_16_from_1[(gray16&0xff) >>
-                      png_ptr->gamma_shift][gray16 >> 8];
-                  rgb_error |= 1;
-               }
-
-               *(dp++) = (png_byte)((w>>8) & 0xff);
-               *(dp++) = (png_byte)(w & 0xff);
-
-               if (have_alpha)
-               {
-                  *(dp++) = *(sp++);
-                  *(dp++) = *(sp++);
-               }
-            }
-         }
-         else
-#endif
-         {
-            png_bytep sp = row;
-            png_bytep dp = row;
-            png_uint_32 i;
-
-            for (i = 0; i < row_width; i++)
-            {
-               png_uint_16 red, green, blue, gray16;
-
-               red   = (png_uint_16)(((*(sp))<<8) | *(sp + 1)); sp += 2;
-               green = (png_uint_16)(((*(sp))<<8) | *(sp + 1)); sp += 2;
-               blue  = (png_uint_16)(((*(sp))<<8) | *(sp + 1)); sp += 2;
-
-               if (red != green || red != blue)
-                  rgb_error |= 1;
-
-               /* From 1.5.5 in the 16 bit case do the accurate conversion even
-                * in the 'fast' case - this is because this is where the code
-                * ends up when handling linear 16 bit data.
-                */
-               gray16  = (png_uint_16)((rc*red + gc*green + bc*blue + 16384) >>
-                  15);
-               *(dp++) = (png_byte)((gray16>>8) & 0xff);
-               *(dp++) = (png_byte)(gray16 & 0xff);
-
-               if (have_alpha)
-               {
-                  *(dp++) = *(sp++);
-                  *(dp++) = *(sp++);
-               }
-            }
-         }
-      }
-
-      row_info->channels = (png_byte)(row_info->channels - 2);
-      row_info->color_type = (png_byte)(row_info->color_type &
-          ~PNG_COLOR_MASK_COLOR);
+   row_info->channels -= (png_byte)2;
+      row_info->color_type &= ~PNG_COLOR_MASK_COLOR;
       row_info->pixel_depth = (png_byte)(row_info->channels *
-          row_info->bit_depth);
+         row_info->bit_depth);
       row_info->rowbytes = PNG_ROWBYTES(row_info->pixel_depth, row_width);
    }
    return rgb_error;
 }
 #endif
-#endif /* PNG_READ_TRANSFORMS_SUPPORTED */
-
-#ifdef PNG_BUILD_GRAYSCALE_PALETTE_SUPPORTED
+
 /* Build a grayscale palette.  Palette is assumed to be 1 << bit_depth
  * large of png_color.  This lets grayscale images be treated as
  * paletted.  Most useful for gamma correction and simplification
- * of code.  This API is not used internally.
+ * of code.
  */
 void PNGAPI
 png_build_grayscale_palette(int bit_depth, png_colorp palette)
 {
    int num_palette;
    int color_inc;
    int i;
    int v;
 
    png_debug(1, "in png_do_build_grayscale_palette");
@@ skipping 29 matching lines @@
          break;
    }
 
    for (i = 0, v = 0; i < num_palette; i++, v += color_inc)
    {
       palette[i].red = (png_byte)v;
       palette[i].green = (png_byte)v;
       palette[i].blue = (png_byte)v;
    }
 }
-#endif
-
-
-#ifdef PNG_READ_TRANSFORMS_SUPPORTED
-#if defined(PNG_READ_BACKGROUND_SUPPORTED) ||\
-   defined(PNG_READ_ALPHA_MODE_SUPPORTED)
+
+/* This function is currently unused.  Do we really need it? */
+#if defined(PNG_READ_DITHER_SUPPORTED) && \
+  defined(PNG_CORRECT_PALETTE_SUPPORTED)
+void /* PRIVATE */
+png_correct_palette(png_structp png_ptr, png_colorp palette,
+   int num_palette)
+{
+   png_debug(1, "in png_correct_palette");
+
+#if defined(PNG_READ_BACKGROUND_SUPPORTED) && \
+    defined(PNG_READ_GAMMA_SUPPORTED) && \
+  defined(PNG_FLOATING_POINT_SUPPORTED)
+   if (png_ptr->transformations & (PNG_GAMMA | PNG_BACKGROUND))
+   {
+      png_color back, back_1;
+
+      if (png_ptr->background_gamma_type == PNG_BACKGROUND_GAMMA_FILE)
+      {
+         back.red = png_ptr->gamma_table[png_ptr->background.red];
+         back.green = png_ptr->gamma_table[png_ptr->background.green];
+         back.blue = png_ptr->gamma_table[png_ptr->background.blue];
+
+         back_1.red = png_ptr->gamma_to_1[png_ptr->background.red];
+         back_1.green = png_ptr->gamma_to_1[png_ptr->background.green];
+         back_1.blue = png_ptr->gamma_to_1[png_ptr->background.blue];
+      }
+      else
+      {
+         double g;
+
+         g = 1.0 / (png_ptr->background_gamma * png_ptr->screen_gamma);
+
+         if (png_ptr->background_gamma_type == PNG_BACKGROUND_GAMMA_SCREEN
+             || fabs(g - 1.0) < PNG_GAMMA_THRESHOLD)
+         {
+            back.red = png_ptr->background.red;
+            back.green = png_ptr->background.green;
+            back.blue = png_ptr->background.blue;
+         }
+         else
+         {
+            back.red =
+               (png_byte)(pow((double)png_ptr->background.red/255, g) *
+                255.0 + 0.5);
+            back.green =
+               (png_byte)(pow((double)png_ptr->background.green/255, g) *
+                255.0 + 0.5);
+            back.blue =
+               (png_byte)(pow((double)png_ptr->background.blue/255, g) *
+                255.0 + 0.5);
+         }
+
+         g = 1.0 / png_ptr->background_gamma;
+
+         back_1.red =
+            (png_byte)(pow((double)png_ptr->background.red/255, g) *
+             255.0 + 0.5);
+         back_1.green =
+            (png_byte)(pow((double)png_ptr->background.green/255, g) *
+             255.0 + 0.5);
+         back_1.blue =
+            (png_byte)(pow((double)png_ptr->background.blue/255, g) *
+             255.0 + 0.5);
+      }
+
+      if (png_ptr->color_type == PNG_COLOR_TYPE_PALETTE)
+      {
+         png_uint_32 i;
+
+         for (i = 0; i < (png_uint_32)num_palette; i++)
+         {
+            if (i < png_ptr->num_trans && png_ptr->trans[i] == 0)
+            {
+               palette[i] = back;
+            }
+            else if (i < png_ptr->num_trans && png_ptr->trans[i] != 0xff)
+            {
+               png_byte v, w;
+
+               v = png_ptr->gamma_to_1[png_ptr->palette[i].red];
+               png_composite(w, v, png_ptr->trans[i], back_1.red);
+               palette[i].red = png_ptr->gamma_from_1[w];
+
+               v = png_ptr->gamma_to_1[png_ptr->palette[i].green];
+               png_composite(w, v, png_ptr->trans[i], back_1.green);
+               palette[i].green = png_ptr->gamma_from_1[w];
+
+               v = png_ptr->gamma_to_1[png_ptr->palette[i].blue];
+               png_composite(w, v, png_ptr->trans[i], back_1.blue);
+               palette[i].blue = png_ptr->gamma_from_1[w];
+            }
+            else
+            {
+               palette[i].red = png_ptr->gamma_table[palette[i].red];
+               palette[i].green = png_ptr->gamma_table[palette[i].green];
+               palette[i].blue = png_ptr->gamma_table[palette[i].blue];
+            }
+         }
+      }
+      else
+      {
+         int i;
+
+         for (i = 0; i < num_palette; i++)
+         {
+            if (palette[i].red == (png_byte)png_ptr->trans_values.gray)
+            {
+               palette[i] = back;
+            }
+            else
+            {
+               palette[i].red = png_ptr->gamma_table[palette[i].red];
+               palette[i].green = png_ptr->gamma_table[palette[i].green];
+               palette[i].blue = png_ptr->gamma_table[palette[i].blue];
+            }
+         }
+      }
+   }
+   else
+#endif
+#ifdef PNG_READ_GAMMA_SUPPORTED
+   if (png_ptr->transformations & PNG_GAMMA)
+   {
+      int i;
+
+      for (i = 0; i < num_palette; i++)
+      {
+         palette[i].red = png_ptr->gamma_table[palette[i].red];
+         palette[i].green = png_ptr->gamma_table[palette[i].green];
+         palette[i].blue = png_ptr->gamma_table[palette[i].blue];
+      }
+   }
+#ifdef PNG_READ_BACKGROUND_SUPPORTED
+   else
+#endif
+#endif
+#ifdef PNG_READ_BACKGROUND_SUPPORTED
+   if (png_ptr->transformations & PNG_BACKGROUND)
+   {
+      if (png_ptr->color_type == PNG_COLOR_TYPE_PALETTE)
+      {
+         png_color back;
+
+         back.red   = (png_byte)png_ptr->background.red;
+         back.green = (png_byte)png_ptr->background.green;
+         back.blue  = (png_byte)png_ptr->background.blue;
+
+         for (i = 0; i < (int)png_ptr->num_trans; i++)
+         {
+            if (png_ptr->trans[i] == 0)
+            {
+               palette[i].red = back.red;
+               palette[i].green = back.green;
+               palette[i].blue = back.blue;
+            }
+            else if (png_ptr->trans[i] != 0xff)
+            {
+               png_composite(palette[i].red, png_ptr->palette[i].red,
+                  png_ptr->trans[i], back.red);
+               png_composite(palette[i].green, png_ptr->palette[i].green,
+                  png_ptr->trans[i], back.green);
+               png_composite(palette[i].blue, png_ptr->palette[i].blue,
+                  png_ptr->trans[i], back.blue);
+            }
+         }
+      }
+      else /* Assume grayscale palette (what else could it be?) */
+      {
+         int i;
+
+         for (i = 0; i < num_palette; i++)
+         {
+            if (i == (png_byte)png_ptr->trans_values.gray)
+            {
+               palette[i].red = (png_byte)png_ptr->background.red;
+               palette[i].green = (png_byte)png_ptr->background.green;
+               palette[i].blue = (png_byte)png_ptr->background.blue;
+            }
+         }
+      }
+   }
+#endif
+}
+#endif
+
+#ifdef PNG_READ_BACKGROUND_SUPPORTED
 /* Replace any alpha or transparency with the supplied background color.
  * "background" is already in the screen gamma, while "background_1" is
  * at a gamma of 1.0.  Paletted files have already been taken care of.
  */
 void /* PRIVATE */
-png_do_compose(png_row_infop row_info, png_bytep row, png_structrp png_ptr)
+png_do_background(png_row_infop row_info, png_bytep row,
+   png_color_16p trans_values, png_color_16p background
+#ifdef PNG_READ_GAMMA_SUPPORTED
+   , png_color_16p background_1,
+   png_bytep gamma_table, png_bytep gamma_from_1, png_bytep gamma_to_1,
+   png_uint_16pp gamma_16, png_uint_16pp gamma_16_from_1,
+   png_uint_16pp gamma_16_to_1, int gamma_shift
+#endif
+   )
 {
-#ifdef PNG_READ_GAMMA_SUPPORTED
-   png_const_bytep gamma_table = png_ptr->gamma_table;
-   png_const_bytep gamma_from_1 = png_ptr->gamma_from_1;
-   png_const_bytep gamma_to_1 = png_ptr->gamma_to_1;
-   png_const_uint_16pp gamma_16 = png_ptr->gamma_16_table;
-   png_const_uint_16pp gamma_16_from_1 = png_ptr->gamma_16_from_1;
-   png_const_uint_16pp gamma_16_to_1 = png_ptr->gamma_16_to_1;
-   int gamma_shift = png_ptr->gamma_shift;
-   int optimize = (png_ptr->flags & PNG_FLAG_OPTIMIZE_ALPHA) != 0;
-#endif
-
-   png_bytep sp;
+   png_bytep sp, dp;
    png_uint_32 i;
-   png_uint_32 row_width = row_info->width;
+   png_uint_32 row_width=row_info->width;
    int shift;
 
-   png_debug(1, "in png_do_compose");
-
+   png_debug(1, "in png_do_background");
+
+   if (background != NULL &&
+#ifdef PNG_USELESS_TESTS_SUPPORTED
+       row != NULL && row_info != NULL &&
+#endif
+      (!(row_info->color_type & PNG_COLOR_MASK_ALPHA) ||
+      (row_info->color_type != PNG_COLOR_TYPE_PALETTE && trans_values)))
    {
       switch (row_info->color_type)
       {
          case PNG_COLOR_TYPE_GRAY:
          {
             switch (row_info->bit_depth)
             {
                case 1:
                {
                   sp = row;
                   shift = 7;
                   for (i = 0; i < row_width; i++)
                   {
                      if ((png_uint_16)((*sp >> shift) & 0x01)
-                        == png_ptr->trans_color.gray)
+                        == trans_values->gray)
                      {
-                        unsigned int tmp = *sp & (0x7f7f >> (7 - shift));
-                        tmp |= png_ptr->background.gray << shift;
-                        *sp = (png_byte)(tmp & 0xff);
+                        *sp &= (png_byte)((0x7f7f >> (7 - shift)) & 0xff);
+                        *sp |= (png_byte)(background->gray << shift);
                      }
-
                      if (!shift)
                      {
                         shift = 7;
                         sp++;
                      }
-
                      else
                         shift--;
                   }
                   break;
                }
 
                case 2:
                {
 #ifdef PNG_READ_GAMMA_SUPPORTED
                   if (gamma_table != NULL)
                   {
                      sp = row;
                      shift = 6;
                      for (i = 0; i < row_width; i++)
                      {
                         if ((png_uint_16)((*sp >> shift) & 0x03)
-                            == png_ptr->trans_color.gray)
+                            == trans_values->gray)
                         {
-                           unsigned int tmp = *sp & (0x3f3f >> (6 - shift));
-                           tmp |= png_ptr->background.gray << shift;
-                           *sp = (png_byte)(tmp & 0xff);
+                           *sp &= (png_byte)((0x3f3f >> (6 - shift)) & 0xff);
+                           *sp |= (png_byte)(background->gray << shift);
                         }
-
                         else
                         {
-                           unsigned int p = (*sp >> shift) & 0x03;
-                           unsigned int g = (gamma_table [p | (p << 2) |
-                               (p << 4) | (p << 6)] >> 6) & 0x03;
-                           unsigned int tmp = *sp & (0x3f3f >> (6 - shift));
-                           tmp |= g << shift;
-                           *sp = (png_byte)(tmp & 0xff);
+                           png_byte p = (png_byte)((*sp >> shift) & 0x03);
+                           png_byte g = (png_byte)((gamma_table [p | (p << 2) |
+                               (p << 4) | (p << 6)] >> 6) & 0x03);
+                           *sp &= (png_byte)((0x3f3f >> (6 - shift)) & 0xff);
+                           *sp |= (png_byte)(g << shift);
                         }
-
                         if (!shift)
                         {
                            shift = 6;
                            sp++;
                         }
-
                         else
                            shift -= 2;
                      }
                   }
-
                   else
 #endif
                   {
                      sp = row;
                      shift = 6;
                      for (i = 0; i < row_width; i++)
                      {
                         if ((png_uint_16)((*sp >> shift) & 0x03)
-                            == png_ptr->trans_color.gray)
+                            == trans_values->gray)
                         {
-                           unsigned int tmp = *sp & (0x3f3f >> (6 - shift));
-                           tmp |= png_ptr->background.gray << shift;
-                           *sp = (png_byte)(tmp & 0xff);
+                           *sp &= (png_byte)((0x3f3f >> (6 - shift)) & 0xff);
+                           *sp |= (png_byte)(background->gray << shift);
                         }
-
                         if (!shift)
                         {
                            shift = 6;
                            sp++;
                         }
-
                         else
                            shift -= 2;
                      }
                   }
                   break;
                }
 
                case 4:
                {
 #ifdef PNG_READ_GAMMA_SUPPORTED
                   if (gamma_table != NULL)
                   {
                      sp = row;
                      shift = 4;
                      for (i = 0; i < row_width; i++)
                      {
                         if ((png_uint_16)((*sp >> shift) & 0x0f)
-                            == png_ptr->trans_color.gray)
+                            == trans_values->gray)
                         {
-                           unsigned int tmp = *sp & (0xf0f >> (4 - shift));
-                           tmp |= png_ptr->background.gray << shift;
-                           *sp = (png_byte)(tmp & 0xff);
+                           *sp &= (png_byte)((0xf0f >> (4 - shift)) & 0xff);
+                           *sp |= (png_byte)(background->gray << shift);
                         }
-
                         else
                         {
-                           unsigned int p = (*sp >> shift) & 0x0f;
-                           unsigned int g = (gamma_table[p | (p << 4)] >> 4) &
-                              0x0f;
-                           unsigned int tmp = *sp & (0xf0f >> (4 - shift));
-                           tmp |= g << shift;
-                           *sp = (png_byte)(tmp & 0xff);
+                           png_byte p = (png_byte)((*sp >> shift) & 0x0f);
+                           png_byte g = (png_byte)((gamma_table[p |
+                             (p << 4)] >> 4) & 0x0f);
+                           *sp &= (png_byte)((0xf0f >> (4 - shift)) & 0xff);
+                           *sp |= (png_byte)(g << shift);
                         }
-
                         if (!shift)
                         {
                            shift = 4;
                            sp++;
                         }
-
                         else
                            shift -= 4;
                      }
                   }
-
                   else
 #endif
                   {
                      sp = row;
                      shift = 4;
                      for (i = 0; i < row_width; i++)
                      {
                         if ((png_uint_16)((*sp >> shift) & 0x0f)
-                            == png_ptr->trans_color.gray)
+                            == trans_values->gray)
                         {
-                           unsigned int tmp = *sp & (0xf0f >> (4 - shift));
-                           tmp |= png_ptr->background.gray << shift;
-                           *sp = (png_byte)(tmp & 0xff);
+                           *sp &= (png_byte)((0xf0f >> (4 - shift)) & 0xff);
+                           *sp |= (png_byte)(background->gray << shift);
                         }
-
                         if (!shift)
                         {
                            shift = 4;
                            sp++;
                         }
-
                         else
                            shift -= 4;
                      }
                   }
                   break;
                }
 
                case 8:
                {
 #ifdef PNG_READ_GAMMA_SUPPORTED
                   if (gamma_table != NULL)
                   {
                      sp = row;
                      for (i = 0; i < row_width; i++, sp++)
                      {
-                        if (*sp == png_ptr->trans_color.gray)
-                           *sp = (png_byte)png_ptr->background.gray;
-
+                        if (*sp == trans_values->gray)
+                        {
+                           *sp = (png_byte)background->gray;
+                        }
                         else
+                        {
                            *sp = gamma_table[*sp];
+                        }
                      }
                   }
                   else
 #endif
                   {
                      sp = row;
                      for (i = 0; i < row_width; i++, sp++)
                      {
-                        if (*sp == png_ptr->trans_color.gray)
-                           *sp = (png_byte)png_ptr->background.gray;
+                        if (*sp == trans_values->gray)
+                        {
+                           *sp = (png_byte)background->gray;
+                        }
                      }
                   }
                   break;
                }
 
                case 16:
                {
 #ifdef PNG_READ_GAMMA_SUPPORTED
                   if (gamma_16 != NULL)
                   {
                      sp = row;
                      for (i = 0; i < row_width; i++, sp += 2)
                      {
                         png_uint_16 v;
 
                         v = (png_uint_16)(((*sp) << 8) + *(sp + 1));
-
-                        if (v == png_ptr->trans_color.gray)
+                        if (v == trans_values->gray)
                         {
                            /* Background is already in screen gamma */
-                           *sp = (png_byte)((png_ptr->background.gray >> 8)
-                                & 0xff);
-                           *(sp + 1) = (png_byte)(png_ptr->background.gray
-                                & 0xff);
+                           *sp = (png_byte)((background->gray >> 8) & 0xff);
+                           *(sp + 1) = (png_byte)(background->gray & 0xff);
                         }
-
                         else
                         {
                            v = gamma_16[*(sp + 1) >> gamma_shift][*sp];
                            *sp = (png_byte)((v >> 8) & 0xff);
                            *(sp + 1) = (png_byte)(v & 0xff);
                         }
                      }
                   }
                   else
 #endif
                   {
                      sp = row;
                      for (i = 0; i < row_width; i++, sp += 2)
                      {
                         png_uint_16 v;
 
                         v = (png_uint_16)(((*sp) << 8) + *(sp + 1));
-
-                        if (v == png_ptr->trans_color.gray)
+                        if (v == trans_values->gray)
                         {
-                           *sp = (png_byte)((png_ptr->background.gray >> 8)
-                                & 0xff);
-                           *(sp + 1) = (png_byte)(png_ptr->background.gray
-                                & 0xff);
+                           *sp = (png_byte)((background->gray >> 8) & 0xff);
+                           *(sp + 1) = (png_byte)(background->gray & 0xff);
                         }
                      }
                   }
                   break;
                }
-
-               default:
-                  break;
             }
             break;
          }
 
          case PNG_COLOR_TYPE_RGB:
          {
             if (row_info->bit_depth == 8)
             {
 #ifdef PNG_READ_GAMMA_SUPPORTED
                if (gamma_table != NULL)
                {
                   sp = row;
                   for (i = 0; i < row_width; i++, sp += 3)
                   {
-                     if (*sp == png_ptr->trans_color.red &&
-                         *(sp + 1) == png_ptr->trans_color.green &&
-                         *(sp + 2) == png_ptr->trans_color.blue)
+                     if (*sp == trans_values->red &&
+                        *(sp + 1) == trans_values->green &&
+                        *(sp + 2) == trans_values->blue)
                      {
-                        *sp = (png_byte)png_ptr->background.red;
-                        *(sp + 1) = (png_byte)png_ptr->background.green;
-                        *(sp + 2) = (png_byte)png_ptr->background.blue;
+                        *sp = (png_byte)background->red;
+                        *(sp + 1) = (png_byte)background->green;
+                        *(sp + 2) = (png_byte)background->blue;
                      }
-
                      else
                      {
                         *sp = gamma_table[*sp];
                         *(sp + 1) = gamma_table[*(sp + 1)];
                         *(sp + 2) = gamma_table[*(sp + 2)];
                      }
                   }
                }
                else
 #endif
                {
                   sp = row;
                   for (i = 0; i < row_width; i++, sp += 3)
                   {
-                     if (*sp == png_ptr->trans_color.red &&
-                         *(sp + 1) == png_ptr->trans_color.green &&
-                         *(sp + 2) == png_ptr->trans_color.blue)
+                     if (*sp == trans_values->red &&
+                        *(sp + 1) == trans_values->green &&
+                        *(sp + 2) == trans_values->blue)
                      {
-                        *sp = (png_byte)png_ptr->background.red;
-                        *(sp + 1) = (png_byte)png_ptr->background.green;
-                        *(sp + 2) = (png_byte)png_ptr->background.blue;
+                        *sp = (png_byte)background->red;
+                        *(sp + 1) = (png_byte)background->green;
+                        *(sp + 2) = (png_byte)background->blue;
                      }
                   }
                }
             }
             else /* if (row_info->bit_depth == 16) */
             {
 #ifdef PNG_READ_GAMMA_SUPPORTED
                if (gamma_16 != NULL)
                {
                   sp = row;
                   for (i = 0; i < row_width; i++, sp += 6)
                   {
                      png_uint_16 r = (png_uint_16)(((*sp) << 8) + *(sp + 1));
-
-                     png_uint_16 g = (png_uint_16)(((*(sp + 2)) << 8)
-                         + *(sp + 3));
-
-                     png_uint_16 b = (png_uint_16)(((*(sp + 4)) << 8)
-                         + *(sp + 5));
-
-                     if (r == png_ptr->trans_color.red &&
-                         g == png_ptr->trans_color.green &&
-                         b == png_ptr->trans_color.blue)
+                     png_uint_16 g = (png_uint_16)(((*(sp+2)) << 8) + *(sp+3));
+                     png_uint_16 b = (png_uint_16)(((*(sp+4)) << 8) + *(sp+5));
+                     if (r == trans_values->red && g == trans_values->green &&
+                        b == trans_values->blue)
                      {
                         /* Background is already in screen gamma */
-                        *sp = (png_byte)((png_ptr->background.red >> 8) & 0xff);
-                        *(sp + 1) = (png_byte)(png_ptr->background.red & 0xff);
-                        *(sp + 2) = (png_byte)((png_ptr->background.green >> 8)
-                                & 0xff);
-                        *(sp + 3) = (png_byte)(png_ptr->background.green
-                                & 0xff);
-                        *(sp + 4) = (png_byte)((png_ptr->background.blue >> 8)
-                                & 0xff);
-                        *(sp + 5) = (png_byte)(png_ptr->background.blue & 0xff);
+                        *sp = (png_byte)((background->red >> 8) & 0xff);
+                        *(sp + 1) = (png_byte)(background->red & 0xff);
+                        *(sp + 2) = (png_byte)((background->green >> 8) & 0xff);
+                        *(sp + 3) = (png_byte)(background->green & 0xff);
+                        *(sp + 4) = (png_byte)((background->blue >> 8) & 0xff);
+                        *(sp + 5) = (png_byte)(background->blue & 0xff);
                      }
-
                      else
                      {
                         png_uint_16 v = gamma_16[*(sp + 1) >> gamma_shift][*sp];
                         *sp = (png_byte)((v >> 8) & 0xff);
                         *(sp + 1) = (png_byte)(v & 0xff);
-
                         v = gamma_16[*(sp + 3) >> gamma_shift][*(sp + 2)];
                         *(sp + 2) = (png_byte)((v >> 8) & 0xff);
                         *(sp + 3) = (png_byte)(v & 0xff);
-
                         v = gamma_16[*(sp + 5) >> gamma_shift][*(sp + 4)];
                         *(sp + 4) = (png_byte)((v >> 8) & 0xff);
                         *(sp + 5) = (png_byte)(v & 0xff);
                      }
                   }
                }
-
                else
 #endif
                {
                   sp = row;
                   for (i = 0; i < row_width; i++, sp += 6)
                   {
-                     png_uint_16 r = (png_uint_16)(((*sp) << 8) + *(sp + 1));
+                     png_uint_16 r = (png_uint_16)(((*sp) << 8) + *(sp+1));
+                     png_uint_16 g = (png_uint_16)(((*(sp+2)) << 8) + *(sp+3));
+                     png_uint_16 b = (png_uint_16)(((*(sp+4)) << 8) + *(sp+5));
 
-                     png_uint_16 g = (png_uint_16)(((*(sp + 2)) << 8)
-                         + *(sp + 3));
-
-                     png_uint_16 b = (png_uint_16)(((*(sp + 4)) << 8)
-                         + *(sp + 5));
-
-                     if (r == png_ptr->trans_color.red &&
-                         g == png_ptr->trans_color.green &&
-                         b == png_ptr->trans_color.blue)
+                     if (r == trans_values->red && g == trans_values->green &&
+                        b == trans_values->blue)
                      {
-                        *sp = (png_byte)((png_ptr->background.red >> 8) & 0xff);
-                        *(sp + 1) = (png_byte)(png_ptr->background.red & 0xff);
-                        *(sp + 2) = (png_byte)((png_ptr->background.green >> 8)
-                                & 0xff);
-                        *(sp + 3) = (png_byte)(png_ptr->background.green
-                                & 0xff);
-                        *(sp + 4) = (png_byte)((png_ptr->background.blue >> 8)
-                                & 0xff);
-                        *(sp + 5) = (png_byte)(png_ptr->background.blue & 0xff);
+                        *sp = (png_byte)((background->red >> 8) & 0xff);
+                        *(sp + 1) = (png_byte)(background->red & 0xff);
+                        *(sp + 2) = (png_byte)((background->green >> 8) & 0xff);
+                        *(sp + 3) = (png_byte)(background->green & 0xff);
+                        *(sp + 4) = (png_byte)((background->blue >> 8) & 0xff);
+                        *(sp + 5) = (png_byte)(background->blue & 0xff);
                      }
                   }
                }
             }
             break;
          }
 
          case PNG_COLOR_TYPE_GRAY_ALPHA:
          {
             if (row_info->bit_depth == 8)
             {
 #ifdef PNG_READ_GAMMA_SUPPORTED
                if (gamma_to_1 != NULL && gamma_from_1 != NULL &&
                    gamma_table != NULL)
                {
                   sp = row;
-                  for (i = 0; i < row_width; i++, sp += 2)
+                  dp = row;
+                  for (i = 0; i < row_width; i++, sp += 2, dp++)
                   {
                      png_uint_16 a = *(sp + 1);
 
                      if (a == 0xff)
-                        *sp = gamma_table[*sp];
-
+                     {
+                        *dp = gamma_table[*sp];
+                     }
                      else if (a == 0)
                      {
                         /* Background is already in screen gamma */
-                        *sp = (png_byte)png_ptr->background.gray;
+                        *dp = (png_byte)background->gray;
                      }
-
                      else
                      {
                         png_byte v, w;
 
                         v = gamma_to_1[*sp];
-                        png_composite(w, v, a, png_ptr->background_1.gray);
-                        if (!optimize)
-                           w = gamma_from_1[w];
-                        *sp = w;
+                        png_composite(w, v, a, background_1->gray);
+                        *dp = gamma_from_1[w];
                      }
                   }
                }
                else
 #endif
                {
                   sp = row;
-                  for (i = 0; i < row_width; i++, sp += 2)
+                  dp = row;
+                  for (i = 0; i < row_width; i++, sp += 2, dp++)
                   {
                      png_byte a = *(sp + 1);
 
-                     if (a == 0)
-                        *sp = (png_byte)png_ptr->background.gray;
-
-                     else if (a < 0xff)
-                        png_composite(*sp, *sp, a, png_ptr->background.gray);
+                     if (a == 0xff)
+                     {
+                        *dp = *sp;
+                     }
+#ifdef PNG_READ_GAMMA_SUPPORTED
+                     else if (a == 0)
+                     {
+                        *dp = (png_byte)background->gray;
+                     }
+                     else
+                     {
+                        png_composite(*dp, *sp, a, background_1->gray);
+                     }
+#else
+                     *dp = (png_byte)background->gray;
+#endif
                   }
                }
             }
             else /* if (png_ptr->bit_depth == 16) */
             {
 #ifdef PNG_READ_GAMMA_SUPPORTED
                if (gamma_16 != NULL && gamma_16_from_1 != NULL &&
                    gamma_16_to_1 != NULL)
                {
                   sp = row;
-                  for (i = 0; i < row_width; i++, sp += 4)
+                  dp = row;
+                  for (i = 0; i < row_width; i++, sp += 4, dp += 2)
                   {
-                     png_uint_16 a = (png_uint_16)(((*(sp + 2)) << 8)
-                         + *(sp + 3));
+                     png_uint_16 a = (png_uint_16)(((*(sp+2)) << 8) + *(sp+3));
 
                      if (a == (png_uint_16)0xffff)
                      {
                         png_uint_16 v;
 
                         v = gamma_16[*(sp + 1) >> gamma_shift][*sp];
-                        *sp = (png_byte)((v >> 8) & 0xff);
-                        *(sp + 1) = (png_byte)(v & 0xff);
+                        *dp = (png_byte)((v >> 8) & 0xff);
+                        *(dp + 1) = (png_byte)(v & 0xff);
                      }
-
+#ifdef PNG_READ_GAMMA_SUPPORTED
                      else if (a == 0)
+#else
+                     else
+#endif
                      {
                         /* Background is already in screen gamma */
-                        *sp = (png_byte)((png_ptr->background.gray >> 8)
-                                & 0xff);
-                        *(sp + 1) = (png_byte)(png_ptr->background.gray & 0xff);
+                        *dp = (png_byte)((background->gray >> 8) & 0xff);
+                        *(dp + 1) = (png_byte)(background->gray & 0xff);
                      }
-
+#ifdef PNG_READ_GAMMA_SUPPORTED
                      else
                      {
                         png_uint_16 g, v, w;
 
                         g = gamma_16_to_1[*(sp + 1) >> gamma_shift][*sp];
-                        png_composite_16(v, g, a, png_ptr->background_1.gray);
-                        if (optimize)
-                           w = v;
-                        else
-                           w = gamma_16_from_1[(v&0xff) >> gamma_shift][v >> 8];
-                        *sp = (png_byte)((w >> 8) & 0xff);
-                        *(sp + 1) = (png_byte)(w & 0xff);
+                        png_composite_16(v, g, a, background_1->gray);
+                        w = gamma_16_from_1[(v&0xff) >> gamma_shift][v >> 8];
+                        *dp = (png_byte)((w >> 8) & 0xff);
+                        *(dp + 1) = (png_byte)(w & 0xff);
                      }
+#endif
                   }
                }
                else
 #endif
                {
                   sp = row;
-                  for (i = 0; i < row_width; i++, sp += 4)
+                  dp = row;
+                  for (i = 0; i < row_width; i++, sp += 4, dp += 2)
                   {
-                     png_uint_16 a = (png_uint_16)(((*(sp + 2)) << 8)
-                         + *(sp + 3));
-
-                     if (a == 0)
+                     png_uint_16 a = (png_uint_16)(((*(sp+2)) << 8) + *(sp+3));
+                     if (a == (png_uint_16)0xffff)
                      {
-                        *sp = (png_byte)((png_ptr->background.gray >> 8)
-                                & 0xff);
-                        *(sp + 1) = (png_byte)(png_ptr->background.gray & 0xff);
+                        png_memcpy(dp, sp, 2);
                      }
-
-                     else if (a < 0xffff)
+#ifdef PNG_READ_GAMMA_SUPPORTED
+                     else if (a == 0)
+#else
+                     else
+#endif
+                     {
+                        *dp = (png_byte)((background->gray >> 8) & 0xff);
+                        *(dp + 1) = (png_byte)(background->gray & 0xff);
+                     }
+#ifdef PNG_READ_GAMMA_SUPPORTED
+                     else
                      {
                         png_uint_16 g, v;
 
                         g = (png_uint_16)(((*sp) << 8) + *(sp + 1));
-                        png_composite_16(v, g, a, png_ptr->background.gray);
-                        *sp = (png_byte)((v >> 8) & 0xff);
-                        *(sp + 1) = (png_byte)(v & 0xff);
+                        png_composite_16(v, g, a, background_1->gray);
+                        *dp = (png_byte)((v >> 8) & 0xff);
+                        *(dp + 1) = (png_byte)(v & 0xff);
                      }
+#endif
                   }
                }
             }
             break;
          }
 
          case PNG_COLOR_TYPE_RGB_ALPHA:
          {
             if (row_info->bit_depth == 8)
             {
 #ifdef PNG_READ_GAMMA_SUPPORTED
                if (gamma_to_1 != NULL && gamma_from_1 != NULL &&
                    gamma_table != NULL)
                {
                   sp = row;
-                  for (i = 0; i < row_width; i++, sp += 4)
+                  dp = row;
+                  for (i = 0; i < row_width; i++, sp += 4, dp += 3)
                   {
                      png_byte a = *(sp + 3);
 
                      if (a == 0xff)
                      {
-                        *sp = gamma_table[*sp];
-                        *(sp + 1) = gamma_table[*(sp + 1)];
-                        *(sp + 2) = gamma_table[*(sp + 2)];
+                        *dp = gamma_table[*sp];
+                        *(dp + 1) = gamma_table[*(sp + 1)];
+                        *(dp + 2) = gamma_table[*(sp + 2)];
                      }
-
                      else if (a == 0)
                      {
                         /* Background is already in screen gamma */
-                        *sp = (png_byte)png_ptr->background.red;
-                        *(sp + 1) = (png_byte)png_ptr->background.green;
-                        *(sp + 2) = (png_byte)png_ptr->background.blue;
+                        *dp = (png_byte)background->red;
+                        *(dp + 1) = (png_byte)background->green;
+                        *(dp + 2) = (png_byte)background->blue;
                      }
-
                      else
                      {
                         png_byte v, w;
 
                         v = gamma_to_1[*sp];
-                        png_composite(w, v, a, png_ptr->background_1.red);
-                        if (!optimize) w = gamma_from_1[w];
-                        *sp = w;
-
+                        png_composite(w, v, a, background_1->red);
+                        *dp = gamma_from_1[w];
                         v = gamma_to_1[*(sp + 1)];
-                        png_composite(w, v, a, png_ptr->background_1.green);
-                        if (!optimize) w = gamma_from_1[w];
-                        *(sp + 1) = w;
-
+                        png_composite(w, v, a, background_1->green);
+                        *(dp + 1) = gamma_from_1[w];
                         v = gamma_to_1[*(sp + 2)];
-                        png_composite(w, v, a, png_ptr->background_1.blue);
-                        if (!optimize) w = gamma_from_1[w];
-                        *(sp + 2) = w;
+                        png_composite(w, v, a, background_1->blue);
+                        *(dp + 2) = gamma_from_1[w];
                      }
                   }
                }
                else
 #endif
                {
                   sp = row;
-                  for (i = 0; i < row_width; i++, sp += 4)
+                  dp = row;
+                  for (i = 0; i < row_width; i++, sp += 4, dp += 3)
                   {
                      png_byte a = *(sp + 3);
 
-                     if (a == 0)
+                     if (a == 0xff)
                      {
-                        *sp = (png_byte)png_ptr->background.red;
-                        *(sp + 1) = (png_byte)png_ptr->background.green;
-                        *(sp + 2) = (png_byte)png_ptr->background.blue;
+                        *dp = *sp;
+                        *(dp + 1) = *(sp + 1);
+                        *(dp + 2) = *(sp + 2);
                      }
-
-                     else if (a < 0xff)
+                     else if (a == 0)
                      {
-                        png_composite(*sp, *sp, a, png_ptr->background.red);
-
-                        png_composite(*(sp + 1), *(sp + 1), a,
-                            png_ptr->background.green);
-
-                        png_composite(*(sp + 2), *(sp + 2), a,
-                            png_ptr->background.blue);
+                        *dp = (png_byte)background->red;
+                        *(dp + 1) = (png_byte)background->green;
+                        *(dp + 2) = (png_byte)background->blue;
+                     }
+                     else
+                     {
+                        png_composite(*dp, *sp, a, background->red);
+                        png_composite(*(dp + 1), *(sp + 1), a,
+                           background->green);
+                        png_composite(*(dp + 2), *(sp + 2), a,
+                           background->blue);
                      }
                   }
                }
             }
             else /* if (row_info->bit_depth == 16) */
             {
 #ifdef PNG_READ_GAMMA_SUPPORTED
                if (gamma_16 != NULL && gamma_16_from_1 != NULL &&
                    gamma_16_to_1 != NULL)
                {
                   sp = row;
-                  for (i = 0; i < row_width; i++, sp += 8)
+                  dp = row;
+                  for (i = 0; i < row_width; i++, sp += 8, dp += 6)
                   {
                      png_uint_16 a = (png_uint_16)(((png_uint_16)(*(sp + 6))
                          << 8) + (png_uint_16)(*(sp + 7)));
-
                      if (a == (png_uint_16)0xffff)
                      {
                         png_uint_16 v;
 
                         v = gamma_16[*(sp + 1) >> gamma_shift][*sp];
-                        *sp = (png_byte)((v >> 8) & 0xff);
-                        *(sp + 1) = (png_byte)(v & 0xff);
-
+                        *dp = (png_byte)((v >> 8) & 0xff);
+                        *(dp + 1) = (png_byte)(v & 0xff);
                         v = gamma_16[*(sp + 3) >> gamma_shift][*(sp + 2)];
-                        *(sp + 2) = (png_byte)((v >> 8) & 0xff);
-                        *(sp + 3) = (png_byte)(v & 0xff);
-
+                        *(dp + 2) = (png_byte)((v >> 8) & 0xff);
+                        *(dp + 3) = (png_byte)(v & 0xff);
                         v = gamma_16[*(sp + 5) >> gamma_shift][*(sp + 4)];
-                        *(sp + 4) = (png_byte)((v >> 8) & 0xff);
-                        *(sp + 5) = (png_byte)(v & 0xff);
+                        *(dp + 4) = (png_byte)((v >> 8) & 0xff);
+                        *(dp + 5) = (png_byte)(v & 0xff);
                      }
-
                      else if (a == 0)
                      {
                         /* Background is already in screen gamma */
-                        *sp = (png_byte)((png_ptr->background.red >> 8) & 0xff);
-                        *(sp + 1) = (png_byte)(png_ptr->background.red & 0xff);
-                        *(sp + 2) = (png_byte)((png_ptr->background.green >> 8)
-                                & 0xff);
-                        *(sp + 3) = (png_byte)(png_ptr->background.green
-                                & 0xff);
-                        *(sp + 4) = (png_byte)((png_ptr->background.blue >> 8)
-                                & 0xff);
-                        *(sp + 5) = (png_byte)(png_ptr->background.blue & 0xff);
+                        *dp = (png_byte)((background->red >> 8) & 0xff);
+                        *(dp + 1) = (png_byte)(background->red & 0xff);
+                        *(dp + 2) = (png_byte)((background->green >> 8) & 0xff);
+                        *(dp + 3) = (png_byte)(background->green & 0xff);
+                        *(dp + 4) = (png_byte)((background->blue >> 8) & 0xff);
+                        *(dp + 5) = (png_byte)(background->blue & 0xff);
                      }
-
                      else
                      {
-                        png_uint_16 v, w;
+                        png_uint_16 v, w, x;
 
                         v = gamma_16_to_1[*(sp + 1) >> gamma_shift][*sp];
-                        png_composite_16(w, v, a, png_ptr->background_1.red);
-                        if (!optimize)
-                           w = gamma_16_from_1[((w&0xff) >> gamma_shift)][w >>
-                                8];
-                        *sp = (png_byte)((w >> 8) & 0xff);
-                        *(sp + 1) = (png_byte)(w & 0xff);
-
+                        png_composite_16(w, v, a, background_1->red);
+                        x = gamma_16_from_1[((w&0xff) >> gamma_shift)][w >> 8];
+                        *dp = (png_byte)((x >> 8) & 0xff);
+                        *(dp + 1) = (png_byte)(x & 0xff);
                         v = gamma_16_to_1[*(sp + 3) >> gamma_shift][*(sp + 2)];
-                        png_composite_16(w, v, a, png_ptr->background_1.green);
-                        if (!optimize)
-                           w = gamma_16_from_1[((w&0xff) >> gamma_shift)][w >>
-                                8];
-
-                        *(sp + 2) = (png_byte)((w >> 8) & 0xff);
-                        *(sp + 3) = (png_byte)(w & 0xff);
-
+                        png_composite_16(w, v, a, background_1->green);
+                        x = gamma_16_from_1[((w&0xff) >> gamma_shift)][w >> 8];
+                        *(dp + 2) = (png_byte)((x >> 8) & 0xff);
+                        *(dp + 3) = (png_byte)(x & 0xff);
                         v = gamma_16_to_1[*(sp + 5) >> gamma_shift][*(sp + 4)];
-                        png_composite_16(w, v, a, png_ptr->background_1.blue);
-                        if (!optimize)
-                           w = gamma_16_from_1[((w&0xff) >> gamma_shift)][w >>
-                                8];
-
-                        *(sp + 4) = (png_byte)((w >> 8) & 0xff);
-                        *(sp + 5) = (png_byte)(w & 0xff);
+                        png_composite_16(w, v, a, background_1->blue);
+                        x = gamma_16_from_1[(w & 0xff) >> gamma_shift][w >> 8];
+                        *(dp + 4) = (png_byte)((x >> 8) & 0xff);
+                        *(dp + 5) = (png_byte)(x & 0xff);
                      }
                   }
                }
-
                else
 #endif
                {
                   sp = row;
-                  for (i = 0; i < row_width; i++, sp += 8)
+                  dp = row;
+                  for (i = 0; i < row_width; i++, sp += 8, dp += 6)
                   {
                      png_uint_16 a = (png_uint_16)(((png_uint_16)(*(sp + 6))
-                         << 8) + (png_uint_16)(*(sp + 7)));
-
-                     if (a == 0)
+                        << 8) + (png_uint_16)(*(sp + 7)));
+                     if (a == (png_uint_16)0xffff)
                      {
-                        *sp = (png_byte)((png_ptr->background.red >> 8) & 0xff);
-                        *(sp + 1) = (png_byte)(png_ptr->background.red & 0xff);
-                        *(sp + 2) = (png_byte)((png_ptr->background.green >> 8)
-                                & 0xff);
-                        *(sp + 3) = (png_byte)(png_ptr->background.green
-                                & 0xff);
-                        *(sp + 4) = (png_byte)((png_ptr->background.blue >> 8)
-                                & 0xff);
-                        *(sp + 5) = (png_byte)(png_ptr->background.blue & 0xff);
+                        png_memcpy(dp, sp, 6);
                      }
-
-                     else if (a < 0xffff)
+                     else if (a == 0)
+                     {
+                        *dp = (png_byte)((background->red >> 8) & 0xff);
+                        *(dp + 1) = (png_byte)(background->red & 0xff);
+                        *(dp + 2) = (png_byte)((background->green >> 8) & 0xff);
+                        *(dp + 3) = (png_byte)(background->green & 0xff);
+                        *(dp + 4) = (png_byte)((background->blue >> 8) & 0xff);
+                        *(dp + 5) = (png_byte)(background->blue & 0xff);
+                     }
+                     else
                      {
                         png_uint_16 v;
 
                         png_uint_16 r = (png_uint_16)(((*sp) << 8) + *(sp + 1));
                         png_uint_16 g = (png_uint_16)(((*(sp + 2)) << 8)
                             + *(sp + 3));
                         png_uint_16 b = (png_uint_16)(((*(sp + 4)) << 8)
                             + *(sp + 5));
 
-                        png_composite_16(v, r, a, png_ptr->background.red);
-                        *sp = (png_byte)((v >> 8) & 0xff);
-                        *(sp + 1) = (png_byte)(v & 0xff);
-
-                        png_composite_16(v, g, a, png_ptr->background.green);
-                        *(sp + 2) = (png_byte)((v >> 8) & 0xff);
-                        *(sp + 3) = (png_byte)(v & 0xff);
-
-                        png_composite_16(v, b, a, png_ptr->background.blue);
-                        *(sp + 4) = (png_byte)((v >> 8) & 0xff);
-                        *(sp + 5) = (png_byte)(v & 0xff);
+                        png_composite_16(v, r, a, background->red);
+                        *dp = (png_byte)((v >> 8) & 0xff);
+                        *(dp + 1) = (png_byte)(v & 0xff);
+                        png_composite_16(v, g, a, background->green);
+                        *(dp + 2) = (png_byte)((v >> 8) & 0xff);
+                        *(dp + 3) = (png_byte)(v & 0xff);
+                        png_composite_16(v, b, a, background->blue);
+                        *(dp + 4) = (png_byte)((v >> 8) & 0xff);
+                        *(dp + 5) = (png_byte)(v & 0xff);
                      }
                   }
                }
             }
             break;
          }
+      }
 
-         default:
-            break;
+      if (row_info->color_type & PNG_COLOR_MASK_ALPHA)
+      {
+         row_info->color_type &= ~PNG_COLOR_MASK_ALPHA;
+         row_info->channels--;
+         row_info->pixel_depth = (png_byte)(row_info->channels *
+            row_info->bit_depth);
+         row_info->rowbytes = PNG_ROWBYTES(row_info->pixel_depth, row_width);
       }
    }
 }
-#endif /* PNG_READ_BACKGROUND_SUPPORTED || PNG_READ_ALPHA_MODE_SUPPORTED */
+#endif
 
 #ifdef PNG_READ_GAMMA_SUPPORTED
 /* Gamma correct the image, avoiding the alpha channel.  Make sure
  * you do this after you deal with the transparency issue on grayscale
  * or RGB images. If your bit depth is 8, use gamma_table, if it
  * is 16, use gamma_16_table and gamma_shift.  Build these with
  * build_gamma_table().
  */
 void /* PRIVATE */
-png_do_gamma(png_row_infop row_info, png_bytep row, png_structrp png_ptr)
+png_do_gamma(png_row_infop row_info, png_bytep row,
+   png_bytep gamma_table, png_uint_16pp gamma_16_table,
+   int gamma_shift)
 {
-   png_const_bytep gamma_table = png_ptr->gamma_table;
-   png_const_uint_16pp gamma_16_table = png_ptr->gamma_16_table;
-   int gamma_shift = png_ptr->gamma_shift;
-
    png_bytep sp;
    png_uint_32 i;
    png_uint_32 row_width=row_info->width;
 
    png_debug(1, "in png_do_gamma");
 
-   if (((row_info->bit_depth <= 8 && gamma_table != NULL) ||
-       (row_info->bit_depth == 16 && gamma_16_table != NULL)))
+   if (
+#ifdef PNG_USELESS_TESTS_SUPPORTED
+       row != NULL && row_info != NULL &&
+#endif
+       ((row_info->bit_depth <= 8 && gamma_table != NULL) ||
+        (row_info->bit_depth == 16 && gamma_16_table != NULL)))
    {
       switch (row_info->color_type)
       {
          case PNG_COLOR_TYPE_RGB:
          {
             if (row_info->bit_depth == 8)
             {
                sp = row;
                for (i = 0; i < row_width; i++)
                {
                   *sp = gamma_table[*sp];
                   sp++;
                   *sp = gamma_table[*sp];
                   sp++;
                   *sp = gamma_table[*sp];
                   sp++;
                }
             }
-
             else /* if (row_info->bit_depth == 16) */
             {
                sp = row;
                for (i = 0; i < row_width; i++)
                {
                   png_uint_16 v;
 
                   v = gamma_16_table[*(sp + 1) >> gamma_shift][*sp];
                   *sp = (png_byte)((v >> 8) & 0xff);
                   *(sp + 1) = (png_byte)(v & 0xff);
                   sp += 2;
-
                   v = gamma_16_table[*(sp + 1) >> gamma_shift][*sp];
                   *sp = (png_byte)((v >> 8) & 0xff);
                   *(sp + 1) = (png_byte)(v & 0xff);
                   sp += 2;
-
                   v = gamma_16_table[*(sp + 1) >> gamma_shift][*sp];
                   *sp = (png_byte)((v >> 8) & 0xff);
                   *(sp + 1) = (png_byte)(v & 0xff);
                   sp += 2;
                }
             }
             break;
          }
 
          case PNG_COLOR_TYPE_RGB_ALPHA:
          {
             if (row_info->bit_depth == 8)
             {
                sp = row;
                for (i = 0; i < row_width; i++)
                {
                   *sp = gamma_table[*sp];
                   sp++;
-
                   *sp = gamma_table[*sp];
                   sp++;
-
                   *sp = gamma_table[*sp];
                   sp++;
-
                   sp++;
                }
             }
-
             else /* if (row_info->bit_depth == 16) */
             {
                sp = row;
                for (i = 0; i < row_width; i++)
                {
                   png_uint_16 v = gamma_16_table[*(sp + 1) >> gamma_shift][*sp];
                   *sp = (png_byte)((v >> 8) & 0xff);
                   *(sp + 1) = (png_byte)(v & 0xff);
                   sp += 2;
-
                   v = gamma_16_table[*(sp + 1) >> gamma_shift][*sp];
                   *sp = (png_byte)((v >> 8) & 0xff);
                   *(sp + 1) = (png_byte)(v & 0xff);
                   sp += 2;
-
                   v = gamma_16_table[*(sp + 1) >> gamma_shift][*sp];
                   *sp = (png_byte)((v >> 8) & 0xff);
                   *(sp + 1) = (png_byte)(v & 0xff);
                   sp += 4;
                }
             }
             break;
          }
 
          case PNG_COLOR_TYPE_GRAY_ALPHA:
          {
             if (row_info->bit_depth == 8)
             {
                sp = row;
                for (i = 0; i < row_width; i++)
                {
                   *sp = gamma_table[*sp];
                   sp += 2;
                }
             }
-
             else /* if (row_info->bit_depth == 16) */
             {
                sp = row;
                for (i = 0; i < row_width; i++)
                {
                   png_uint_16 v = gamma_16_table[*(sp + 1) >> gamma_shift][*sp];
                   *sp = (png_byte)((v >> 8) & 0xff);
                   *(sp + 1) = (png_byte)(v & 0xff);
                   sp += 4;
                }
@@ skipping 52 matching lines @@
                for (i = 0; i < row_width; i++)
                {
                   png_uint_16 v = gamma_16_table[*(sp + 1) >> gamma_shift][*sp];
                   *sp = (png_byte)((v >> 8) & 0xff);
                   *(sp + 1) = (png_byte)(v & 0xff);
                   sp += 2;
                }
             }
             break;
          }
-
-         default:
-            break;
       }
    }
 }
 #endif
 
-#ifdef PNG_READ_ALPHA_MODE_SUPPORTED
-/* Encode the alpha channel to the output gamma (the input channel is always
- * linear.)  Called only with color types that have an alpha channel.  Needs the
- * from_1 tables.
- */
-void /* PRIVATE */
-png_do_encode_alpha(png_row_infop row_info, png_bytep row, png_structrp png_ptr)
-{
-   png_uint_32 row_width = row_info->width;
-
-   png_debug(1, "in png_do_encode_alpha");
-
-   if (row_info->color_type & PNG_COLOR_MASK_ALPHA)
-   {
-      if (row_info->bit_depth == 8)
-      {
-         PNG_CONST png_bytep table = png_ptr->gamma_from_1;
-
-         if (table != NULL)
-         {
-            PNG_CONST int step =
-               (row_info->color_type & PNG_COLOR_MASK_COLOR) ? 4 : 2;
-
-            /* The alpha channel is the last component: */
-            row += step - 1;
-
-            for (; row_width > 0; --row_width, row += step)
-               *row = table[*row];
-
-            return;
-         }
-      }
-
-      else if (row_info->bit_depth == 16)
-      {
-         PNG_CONST png_uint_16pp table = png_ptr->gamma_16_from_1;
-         PNG_CONST int gamma_shift = png_ptr->gamma_shift;
-
-         if (table != NULL)
-         {
-            PNG_CONST int step =
-               (row_info->color_type & PNG_COLOR_MASK_COLOR) ? 8 : 4;
-
-            /* The alpha channel is the last component: */
-            row += step - 2;
-
-            for (; row_width > 0; --row_width, row += step)
-            {
-               png_uint_16 v;
-
-               v = table[*(row + 1) >> gamma_shift][*row];
-               *row = (png_byte)((v >> 8) & 0xff);
-               *(row + 1) = (png_byte)(v & 0xff);
-            }
-
-            return;
-         }
-      }
-   }
-
-   /* Only get to here if called with a weird row_info; no harm has been done,
-    * so just issue a warning.
-    */
-   png_warning(png_ptr, "png_do_encode_alpha: unexpected call");
-}
-#endif
-
 #ifdef PNG_READ_EXPAND_SUPPORTED
 /* Expands a palette row to an RGB or RGBA row depending
  * upon whether you supply trans and num_trans.
  */
 void /* PRIVATE */
 png_do_expand_palette(png_row_infop row_info, png_bytep row,
-   png_const_colorp palette, png_const_bytep trans_alpha, int num_trans)
+   png_colorp palette, png_bytep trans, int num_trans)
 {
    int shift, value;
    png_bytep sp, dp;
    png_uint_32 i;
    png_uint_32 row_width=row_info->width;
 
    png_debug(1, "in png_do_expand_palette");
 
-   if (row_info->color_type == PNG_COLOR_TYPE_PALETTE)
+   if (
+#ifdef PNG_USELESS_TESTS_SUPPORTED
+       row != NULL && row_info != NULL &&
+#endif
+       row_info->color_type == PNG_COLOR_TYPE_PALETTE)
    {
       if (row_info->bit_depth < 8)
       {
          switch (row_info->bit_depth)
          {
             case 1:
             {
                sp = row + (png_size_t)((row_width - 1) >> 3);
                dp = row + (png_size_t)row_width - 1;
                shift = 7 - (int)((row_width + 7) & 0x07);
                for (i = 0; i < row_width; i++)
                {
                   if ((*sp >> shift) & 0x01)
                      *dp = 1;
-
                   else
                      *dp = 0;
-
                   if (shift == 7)
                   {
                      shift = 0;
                      sp--;
                   }
-
                   else
                      shift++;
 
                   dp--;
                }
                break;
             }
 
             case 2:
             {
                sp = row + (png_size_t)((row_width - 1) >> 2);
                dp = row + (png_size_t)row_width - 1;
                shift = (int)((3 - ((row_width + 3) & 0x03)) << 1);
                for (i = 0; i < row_width; i++)
                {
                   value = (*sp >> shift) & 0x03;
                   *dp = (png_byte)value;
                   if (shift == 6)
                   {
                      shift = 0;
                      sp--;
                   }
-
                   else
                      shift += 2;
 
                   dp--;
                }
                break;
             }
 
             case 4:
             {
                sp = row + (png_size_t)((row_width - 1) >> 1);
                dp = row + (png_size_t)row_width - 1;
                shift = (int)((row_width & 0x01) << 2);
                for (i = 0; i < row_width; i++)
                {
                   value = (*sp >> shift) & 0x0f;
                   *dp = (png_byte)value;
                   if (shift == 4)
                   {
                      shift = 0;
                      sp--;
                   }
-
                   else
                      shift += 4;
 
                   dp--;
                }
                break;
             }
-
-            default:
-               break;
          }
          row_info->bit_depth = 8;
          row_info->pixel_depth = 8;
          row_info->rowbytes = row_width;
       }
-
-      if (row_info->bit_depth == 8)
+      switch (row_info->bit_depth)
       {
+         case 8:
          {
-            if (num_trans > 0)
+            if (trans != NULL)
             {
                sp = row + (png_size_t)row_width - 1;
                dp = row + (png_size_t)(row_width << 2) - 1;
 
                for (i = 0; i < row_width; i++)
                {
                   if ((int)(*sp) >= num_trans)
                      *dp-- = 0xff;
-
                   else
-                     *dp-- = trans_alpha[*sp];
-
+                     *dp-- = trans[*sp];
                   *dp-- = palette[*sp].blue;
                   *dp-- = palette[*sp].green;
                   *dp-- = palette[*sp].red;
                   sp--;
                }
                row_info->bit_depth = 8;
                row_info->pixel_depth = 32;
                row_info->rowbytes = row_width * 4;
                row_info->color_type = 6;
                row_info->channels = 4;
             }
-
             else
             {
                sp = row + (png_size_t)row_width - 1;
                dp = row + (png_size_t)(row_width * 3) - 1;
 
                for (i = 0; i < row_width; i++)
                {
                   *dp-- = palette[*sp].blue;
                   *dp-- = palette[*sp].green;
                   *dp-- = palette[*sp].red;
                   sp--;
                }
 
                row_info->bit_depth = 8;
                row_info->pixel_depth = 24;
                row_info->rowbytes = row_width * 3;
                row_info->color_type = 2;
                row_info->channels = 3;
             }
+            break;
          }
       }
    }
 }
 
 /* If the bit depth < 8, it is expanded to 8.  Also, if the already
  * expanded transparency value is supplied, an alpha channel is built.
  */
 void /* PRIVATE */
 png_do_expand(png_row_infop row_info, png_bytep row,
-    png_const_color_16p trans_color)
+   png_color_16p trans_value)
 {
    int shift, value;
    png_bytep sp, dp;
    png_uint_32 i;
    png_uint_32 row_width=row_info->width;
 
    png_debug(1, "in png_do_expand");
 
+#ifdef PNG_USELESS_TESTS_SUPPORTED
+   if (row != NULL && row_info != NULL)
+#endif
    {
       if (row_info->color_type == PNG_COLOR_TYPE_GRAY)
       {
-         unsigned int gray = trans_color ? trans_color->gray : 0;
+         png_uint_16 gray = (png_uint_16)(trans_value ? trans_value->gray : 0);
 
          if (row_info->bit_depth < 8)
          {
             switch (row_info->bit_depth)
             {
                case 1:
                {
-                  gray = (gray & 0x01) * 0xff;
+                  gray = (png_uint_16)((gray&0x01)*0xff);
                   sp = row + (png_size_t)((row_width - 1) >> 3);
                   dp = row + (png_size_t)row_width - 1;
                   shift = 7 - (int)((row_width + 7) & 0x07);
                   for (i = 0; i < row_width; i++)
                   {
                      if ((*sp >> shift) & 0x01)
                         *dp = 0xff;
-
                      else
                         *dp = 0;
-
                      if (shift == 7)
                      {
                         shift = 0;
                         sp--;
                      }
-
                      else
                         shift++;
 
                      dp--;
                   }
                   break;
                }
 
                case 2:
                {
-                  gray = (gray & 0x03) * 0x55;
+                  gray = (png_uint_16)((gray&0x03)*0x55);
                   sp = row + (png_size_t)((row_width - 1) >> 2);
                   dp = row + (png_size_t)row_width - 1;
                   shift = (int)((3 - ((row_width + 3) & 0x03)) << 1);
                   for (i = 0; i < row_width; i++)
                   {
                      value = (*sp >> shift) & 0x03;
                      *dp = (png_byte)(value | (value << 2) | (value << 4) |
                         (value << 6));
                      if (shift == 6)
                      {
                         shift = 0;
                         sp--;
                      }
-
                      else
                         shift += 2;
 
                      dp--;
                   }
                   break;
                }
 
                case 4:
                {
-                  gray = (gray & 0x0f) * 0x11;
+                  gray = (png_uint_16)((gray&0x0f)*0x11);
                   sp = row + (png_size_t)((row_width - 1) >> 1);
                   dp = row + (png_size_t)row_width - 1;
                   shift = (int)((1 - ((row_width + 1) & 0x01)) << 2);
                   for (i = 0; i < row_width; i++)
                   {
                      value = (*sp >> shift) & 0x0f;
                      *dp = (png_byte)(value | (value << 4));
                      if (shift == 4)
                      {
                         shift = 0;
                         sp--;
                      }
-
                      else
                         shift = 4;
 
                      dp--;
                   }
                   break;
                }
-
-               default:
-                  break;
             }
 
             row_info->bit_depth = 8;
             row_info->pixel_depth = 8;
             row_info->rowbytes = row_width;
          }
 
-         if (trans_color != NULL)
+         if (trans_value != NULL)
          {
             if (row_info->bit_depth == 8)
             {
                gray = gray & 0xff;
                sp = row + (png_size_t)row_width - 1;
                dp = row + (png_size_t)(row_width << 1) - 1;
-
                for (i = 0; i < row_width; i++)
                {
                   if (*sp == gray)
                      *dp-- = 0;
-
                   else
                      *dp-- = 0xff;
-
                   *dp-- = *sp--;
                }
             }
 
             else if (row_info->bit_depth == 16)
             {
-               unsigned int gray_high = (gray >> 8) & 0xff;
-               unsigned int gray_low = gray & 0xff;
+               png_byte gray_high = (gray >> 8) & 0xff;
+               png_byte gray_low = gray & 0xff;
                sp = row + row_info->rowbytes - 1;
                dp = row + (row_info->rowbytes << 1) - 1;
                for (i = 0; i < row_width; i++)
                {
                   if (*(sp - 1) == gray_high && *(sp) == gray_low)
                   {
                      *dp-- = 0;
                      *dp-- = 0;
                   }
-
                   else
                   {
                      *dp-- = 0xff;
                      *dp-- = 0xff;
                   }
-
                   *dp-- = *sp--;
                   *dp-- = *sp--;
                }
             }
 
             row_info->color_type = PNG_COLOR_TYPE_GRAY_ALPHA;
             row_info->channels = 2;
             row_info->pixel_depth = (png_byte)(row_info->bit_depth << 1);
             row_info->rowbytes = PNG_ROWBYTES(row_info->pixel_depth,
                row_width);
          }
       }
-      else if (row_info->color_type == PNG_COLOR_TYPE_RGB && trans_color)
+      else if (row_info->color_type == PNG_COLOR_TYPE_RGB && trans_value)
       {
          if (row_info->bit_depth == 8)
          {
-            png_byte red = (png_byte)(trans_color->red & 0xff);
-            png_byte green = (png_byte)(trans_color->green & 0xff);
-            png_byte blue = (png_byte)(trans_color->blue & 0xff);
+            png_byte red = trans_value->red & 0xff;
+            png_byte green = trans_value->green & 0xff;
+            png_byte blue = trans_value->blue & 0xff;
             sp = row + (png_size_t)row_info->rowbytes - 1;
             dp = row + (png_size_t)(row_width << 2) - 1;
             for (i = 0; i < row_width; i++)
             {
                if (*(sp - 2) == red && *(sp - 1) == green && *(sp) == blue)
                   *dp-- = 0;
-
                else
                   *dp-- = 0xff;
-
                *dp-- = *sp--;
                *dp-- = *sp--;
                *dp-- = *sp--;
             }
          }
          else if (row_info->bit_depth == 16)
          {
-            png_byte red_high = (png_byte)((trans_color->red >> 8) & 0xff);
-            png_byte green_high = (png_byte)((trans_color->green >> 8) & 0xff);
-            png_byte blue_high = (png_byte)((trans_color->blue >> 8) & 0xff);
-            png_byte red_low = (png_byte)(trans_color->red & 0xff);
-            png_byte green_low = (png_byte)(trans_color->green & 0xff);
-            png_byte blue_low = (png_byte)(trans_color->blue & 0xff);
+            png_byte red_high = (trans_value->red >> 8) & 0xff;
+            png_byte green_high = (trans_value->green >> 8) & 0xff;
+            png_byte blue_high = (trans_value->blue >> 8) & 0xff;
+            png_byte red_low = trans_value->red & 0xff;
+            png_byte green_low = trans_value->green & 0xff;
+            png_byte blue_low = trans_value->blue & 0xff;
             sp = row + row_info->rowbytes - 1;
             dp = row + (png_size_t)(row_width << 3) - 1;
             for (i = 0; i < row_width; i++)
             {
                if (*(sp - 5) == red_high &&
-                   *(sp - 4) == red_low &&
-                   *(sp - 3) == green_high &&
-                   *(sp - 2) == green_low &&
-                   *(sp - 1) == blue_high &&
-                   *(sp    ) == blue_low)
+                  *(sp - 4) == red_low &&
+                  *(sp - 3) == green_high &&
+                  *(sp - 2) == green_low &&
+                  *(sp - 1) == blue_high &&
+                  *(sp    ) == blue_low)
                {
                   *dp-- = 0;
                   *dp-- = 0;
                }
-
                else
                {
                   *dp-- = 0xff;
                   *dp-- = 0xff;
                }
-
                *dp-- = *sp--;
                *dp-- = *sp--;
                *dp-- = *sp--;
                *dp-- = *sp--;
                *dp-- = *sp--;
                *dp-- = *sp--;
             }
          }
          row_info->color_type = PNG_COLOR_TYPE_RGB_ALPHA;
          row_info->channels = 4;
          row_info->pixel_depth = (png_byte)(row_info->bit_depth << 2);
          row_info->rowbytes = PNG_ROWBYTES(row_info->pixel_depth, row_width);
       }
    }
 }
 #endif
 
-#ifdef PNG_READ_EXPAND_16_SUPPORTED
-/* If the bit depth is 8 and the color type is not a palette type expand the
- * whole row to 16 bits.  Has no effect otherwise.
- */
+#ifdef PNG_READ_DITHER_SUPPORTED
 void /* PRIVATE */
-png_do_expand_16(png_row_infop row_info, png_bytep row)
-{
-   if (row_info->bit_depth == 8 &&
-      row_info->color_type != PNG_COLOR_TYPE_PALETTE)
-   {
-      /* The row have a sequence of bytes containing [0..255] and we need
-       * to turn it into another row containing [0..65535], to do this we
-       * calculate:
-       *
-       *  (input / 255) * 65535
-       *
-       *  Which happens to be exactly input * 257 and this can be achieved
-       *  simply by byte replication in place (copying backwards).
-       */
-      png_byte *sp = row + row_info->rowbytes; /* source, last byte + 1 */
-      png_byte *dp = sp + row_info->rowbytes;  /* destination, end + 1 */
-      while (dp > sp)
-         dp[-2] = dp[-1] = *--sp, dp -= 2;
-
-      row_info->rowbytes *= 2;
-      row_info->bit_depth = 16;
-      row_info->pixel_depth = (png_byte)(row_info->channels * 16);
-   }
-}
-#endif
-
-#ifdef PNG_READ_QUANTIZE_SUPPORTED
-void /* PRIVATE */
-png_do_quantize(png_row_infop row_info, png_bytep row,
-    png_const_bytep palette_lookup, png_const_bytep quantize_lookup)
+png_do_dither(png_row_infop row_info, png_bytep row,
+    png_bytep palette_lookup, png_bytep dither_lookup)
 {
    png_bytep sp, dp;
    png_uint_32 i;
    png_uint_32 row_width=row_info->width;
 
-   png_debug(1, "in png_do_quantize");
+   png_debug(1, "in png_do_dither");
 
-   if (row_info->bit_depth == 8)
+#ifdef PNG_USELESS_TESTS_SUPPORTED
+   if (row != NULL && row_info != NULL)
+#endif
    {
-      if (row_info->color_type == PNG_COLOR_TYPE_RGB && palette_lookup)
+      if (row_info->color_type == PNG_COLOR_TYPE_RGB &&
+         palette_lookup && row_info->bit_depth == 8)
       {
          int r, g, b, p;
          sp = row;
          dp = row;
          for (i = 0; i < row_width; i++)
          {
             r = *sp++;
             g = *sp++;
             b = *sp++;
 
             /* This looks real messy, but the compiler will reduce
              * it down to a reasonable formula.  For example, with
              * 5 bits per color, we get:
              * p = (((r >> 3) & 0x1f) << 10) |
              *    (((g >> 3) & 0x1f) << 5) |
              *    ((b >> 3) & 0x1f);
              */
-            p = (((r >> (8 - PNG_QUANTIZE_RED_BITS)) &
-                ((1 << PNG_QUANTIZE_RED_BITS) - 1)) <<
-                (PNG_QUANTIZE_GREEN_BITS + PNG_QUANTIZE_BLUE_BITS)) |
-                (((g >> (8 - PNG_QUANTIZE_GREEN_BITS)) &
-                ((1 << PNG_QUANTIZE_GREEN_BITS) - 1)) <<
-                (PNG_QUANTIZE_BLUE_BITS)) |
-                ((b >> (8 - PNG_QUANTIZE_BLUE_BITS)) &
-                ((1 << PNG_QUANTIZE_BLUE_BITS) - 1));
+            p = (((r >> (8 - PNG_DITHER_RED_BITS)) &
+               ((1 << PNG_DITHER_RED_BITS) - 1)) <<
+               (PNG_DITHER_GREEN_BITS + PNG_DITHER_BLUE_BITS)) |
+               (((g >> (8 - PNG_DITHER_GREEN_BITS)) &
+               ((1 << PNG_DITHER_GREEN_BITS) - 1)) <<
+               (PNG_DITHER_BLUE_BITS)) |
+               ((b >> (8 - PNG_DITHER_BLUE_BITS)) &
+               ((1 << PNG_DITHER_BLUE_BITS) - 1));
 
             *dp++ = palette_lookup[p];
          }
-
          row_info->color_type = PNG_COLOR_TYPE_PALETTE;
          row_info->channels = 1;
          row_info->pixel_depth = row_info->bit_depth;
          row_info->rowbytes = PNG_ROWBYTES(row_info->pixel_depth, row_width);
       }
-
       else if (row_info->color_type == PNG_COLOR_TYPE_RGB_ALPHA &&
-         palette_lookup != NULL)
+         palette_lookup != NULL && row_info->bit_depth == 8)
       {
          int r, g, b, p;
          sp = row;
          dp = row;
          for (i = 0; i < row_width; i++)
          {
             r = *sp++;
             g = *sp++;
             b = *sp++;
             sp++;
 
-            p = (((r >> (8 - PNG_QUANTIZE_RED_BITS)) &
-                ((1 << PNG_QUANTIZE_RED_BITS) - 1)) <<
-                (PNG_QUANTIZE_GREEN_BITS + PNG_QUANTIZE_BLUE_BITS)) |
-                (((g >> (8 - PNG_QUANTIZE_GREEN_BITS)) &
-                ((1 << PNG_QUANTIZE_GREEN_BITS) - 1)) <<
-                (PNG_QUANTIZE_BLUE_BITS)) |
-                ((b >> (8 - PNG_QUANTIZE_BLUE_BITS)) &
-                ((1 << PNG_QUANTIZE_BLUE_BITS) - 1));
+            p = (((r >> (8 - PNG_DITHER_RED_BITS)) &
+               ((1 << PNG_DITHER_RED_BITS) - 1)) <<
+               (PNG_DITHER_GREEN_BITS + PNG_DITHER_BLUE_BITS)) |
+               (((g >> (8 - PNG_DITHER_GREEN_BITS)) &
+               ((1 << PNG_DITHER_GREEN_BITS) - 1)) <<
+               (PNG_DITHER_BLUE_BITS)) |
+               ((b >> (8 - PNG_DITHER_BLUE_BITS)) &
+               ((1 << PNG_DITHER_BLUE_BITS) - 1));
 
             *dp++ = palette_lookup[p];
          }
-
          row_info->color_type = PNG_COLOR_TYPE_PALETTE;
          row_info->channels = 1;
          row_info->pixel_depth = row_info->bit_depth;
          row_info->rowbytes = PNG_ROWBYTES(row_info->pixel_depth, row_width);
       }
-
       else if (row_info->color_type == PNG_COLOR_TYPE_PALETTE &&
-         quantize_lookup)
+         dither_lookup && row_info->bit_depth == 8)
       {
          sp = row;
-
          for (i = 0; i < row_width; i++, sp++)
          {
-            *sp = quantize_lookup[*sp];
+            *sp = dither_lookup[*sp];
          }
       }
    }
 }
-#endif /* PNG_READ_QUANTIZE_SUPPORTED */
-#endif /* PNG_READ_TRANSFORMS_SUPPORTED */
+#endif
+
+#ifdef PNG_FLOATING_POINT_SUPPORTED
+#ifdef PNG_READ_GAMMA_SUPPORTED
+static PNG_CONST int png_gamma_shift[] =
+   {0x10, 0x21, 0x42, 0x84, 0x110, 0x248, 0x550, 0xff0, 0x00};
+
+/* We build the 8- or 16-bit gamma tables here.  Note that for 16-bit
+ * tables, we don't make a full table if we are reducing to 8-bit in
+ * the future.  Note also how the gamma_16 tables are segmented so that
+ * we don't need to allocate > 64K chunks for a full 16-bit table.
+ *
+ * See the PNG extensions document for an integer algorithm for creating
+ * the gamma tables.  Maybe we will implement that here someday.
+ *
+ * We should only reach this point if
+ *
+ *      the file_gamma is known (i.e., the gAMA or sRGB chunk is present,
+ *      or the application has provided a file_gamma)
+ *
+ *   AND
+ *      {
+ *         the screen_gamma is known
+ *      OR
+ *
+ *         RGB_to_gray transformation is being performed
+ *      }
+ *
+ *   AND
+ *      {
+ *         the screen_gamma is different from the reciprocal of the
+ *         file_gamma by more than the specified threshold
+ *
+ *      OR
+ *
+ *         a background color has been specified and the file_gamma
+ *         and screen_gamma are not 1.0, within the specified threshold.
+ *      }
+ */
+
+void /* PRIVATE */
+png_build_gamma_table(png_structp png_ptr)
+{
+  png_debug(1, "in png_build_gamma_table");
+
+  if (png_ptr->bit_depth <= 8)
+  {
+     int i;
+     double g;
+
+     if (png_ptr->screen_gamma > .000001)
+        g = 1.0 / (png_ptr->gamma * png_ptr->screen_gamma);
+
+     else
+        g = 1.0;
+
+     png_ptr->gamma_table = (png_bytep)png_malloc(png_ptr,
+        (png_uint_32)256);
+
+     for (i = 0; i < 256; i++)
+     {
+        png_ptr->gamma_table[i] = (png_byte)(pow((double)i / 255.0,
+           g) * 255.0 + .5);
+     }
+
+#if defined(PNG_READ_BACKGROUND_SUPPORTED) || \
+   defined(PNG_READ_RGB_TO_GRAY_SUPPORTED)
+     if (png_ptr->transformations & ((PNG_BACKGROUND) | PNG_RGB_TO_GRAY))
+     {
+
+        g = 1.0 / (png_ptr->gamma);
+
+        png_ptr->gamma_to_1 = (png_bytep)png_malloc(png_ptr,
+           (png_uint_32)256);
+
+        for (i = 0; i < 256; i++)
+        {
+           png_ptr->gamma_to_1[i] = (png_byte)(pow((double)i / 255.0,
+              g) * 255.0 + .5);
+        }
+
+
+        png_ptr->gamma_from_1 = (png_bytep)png_malloc(png_ptr,
+           (png_uint_32)256);
+
+        if (png_ptr->screen_gamma > 0.000001)
+           g = 1.0 / png_ptr->screen_gamma;
+
+        else
+           g = png_ptr->gamma;   /* Probably doing rgb_to_gray */
+
+        for (i = 0; i < 256; i++)
+        {
+           png_ptr->gamma_from_1[i] = (png_byte)(pow((double)i / 255.0,
+              g) * 255.0 + .5);
+
+        }
+     }
+#endif /* PNG_READ_BACKGROUND_SUPPORTED || PNG_RGB_TO_GRAY_SUPPORTED */
+  }
+  else
+  {
+     double g;
+     int i, j, shift, num;
+     int sig_bit;
+     png_uint_32 ig;
+
+     if (png_ptr->color_type & PNG_COLOR_MASK_COLOR)
+     {
+        sig_bit = (int)png_ptr->sig_bit.red;
+
+        if ((int)png_ptr->sig_bit.green > sig_bit)
+           sig_bit = png_ptr->sig_bit.green;
+
+        if ((int)png_ptr->sig_bit.blue > sig_bit)
+           sig_bit = png_ptr->sig_bit.blue;
+     }
+     else
+     {
+        sig_bit = (int)png_ptr->sig_bit.gray;
+     }
+
+     if (sig_bit > 0)
+        shift = 16 - sig_bit;
+
+     else
+        shift = 0;
+
+     if (png_ptr->transformations & PNG_16_TO_8)
+     {
+        if (shift < (16 - PNG_MAX_GAMMA_8))
+           shift = (16 - PNG_MAX_GAMMA_8);
+     }
+
+     if (shift > 8)
+        shift = 8;
+
+     if (shift < 0)
+        shift = 0;
+
+     png_ptr->gamma_shift = (png_byte)shift;
+
+     num = (1 << (8 - shift));
+
+     if (png_ptr->screen_gamma > .000001)
+        g = 1.0 / (png_ptr->gamma * png_ptr->screen_gamma);
+     else
+        g = 1.0;
+
+     png_ptr->gamma_16_table = (png_uint_16pp)png_calloc(png_ptr,
+        (png_uint_32)(num * png_sizeof(png_uint_16p)));
+
+     if (png_ptr->transformations & (PNG_16_TO_8 | PNG_BACKGROUND))
+     {
+        double fin, fout;
+        png_uint_32 last, max;
+
+        for (i = 0; i < num; i++)
+        {
+           png_ptr->gamma_16_table[i] = (png_uint_16p)png_malloc(png_ptr,
+              (png_uint_32)(256 * png_sizeof(png_uint_16)));
+        }
+
+        g = 1.0 / g;
+        last = 0;
+        for (i = 0; i < 256; i++)
+        {
+           fout = ((double)i + 0.5) / 256.0;
+           fin = pow(fout, g);
+           max = (png_uint_32)(fin * (double)((png_uint_32)num << 8));
+           while (last <= max)
+           {
+              png_ptr->gamma_16_table[(int)(last & (0xff >> shift))]
+                 [(int)(last >> (8 - shift))] = (png_uint_16)(
+                 (png_uint_16)i | ((png_uint_16)i << 8));
+              last++;
+           }
+        }
+        while (last < ((png_uint_32)num << 8))
+        {
+           png_ptr->gamma_16_table[(int)(last & (0xff >> shift))]
+              [(int)(last >> (8 - shift))] = (png_uint_16)65535L;
+           last++;
+        }
+     }
+     else
+     {
+        for (i = 0; i < num; i++)
+        {
+           png_ptr->gamma_16_table[i] = (png_uint_16p)png_malloc(png_ptr,
+              (png_uint_32)(256 * png_sizeof(png_uint_16)));
+
+           ig = (((png_uint_32)i * (png_uint_32)png_gamma_shift[shift]) >> 4);
+
+           for (j = 0; j < 256; j++)
+           {
+              png_ptr->gamma_16_table[i][j] =
+                 (png_uint_16)(pow((double)(ig + ((png_uint_32)j << 8)) /
+                    65535.0, g) * 65535.0 + .5);
+           }
+        }
+     }
+
+#if defined(PNG_READ_BACKGROUND_SUPPORTED) || \
+   defined(PNG_READ_RGB_TO_GRAY_SUPPORTED)
+     if (png_ptr->transformations & (PNG_BACKGROUND | PNG_RGB_TO_GRAY))
+     {
+
+        g = 1.0 / (png_ptr->gamma);
+
+        png_ptr->gamma_16_to_1 = (png_uint_16pp)png_calloc(png_ptr,
+           (png_uint_32)(num * png_sizeof(png_uint_16p )));
+
+        for (i = 0; i < num; i++)
+        {
+           png_ptr->gamma_16_to_1[i] = (png_uint_16p)png_malloc(png_ptr,
+              (png_uint_32)(256 * png_sizeof(png_uint_16)));
+
+           ig = (((png_uint_32)i *
+              (png_uint_32)png_gamma_shift[shift]) >> 4);
+           for (j = 0; j < 256; j++)
+           {
+              png_ptr->gamma_16_to_1[i][j] =
+                 (png_uint_16)(pow((double)(ig + ((png_uint_32)j << 8)) /
+                    65535.0, g) * 65535.0 + .5);
+           }
+        }
+
+        if (png_ptr->screen_gamma > 0.000001)
+           g = 1.0 / png_ptr->screen_gamma;
+
+        else
+           g = png_ptr->gamma;   /* Probably doing rgb_to_gray */
+
+        png_ptr->gamma_16_from_1 = (png_uint_16pp)png_calloc(png_ptr,
+           (png_uint_32)(num * png_sizeof(png_uint_16p)));
+
+        for (i = 0; i < num; i++)
+        {
+           png_ptr->gamma_16_from_1[i] = (png_uint_16p)png_malloc(png_ptr,
+              (png_uint_32)(256 * png_sizeof(png_uint_16)));
+
+           ig = (((png_uint_32)i *
+              (png_uint_32)png_gamma_shift[shift]) >> 4);
+
+           for (j = 0; j < 256; j++)
+           {
+              png_ptr->gamma_16_from_1[i][j] =
+                 (png_uint_16)(pow((double)(ig + ((png_uint_32)j << 8)) /
+                    65535.0, g) * 65535.0 + .5);
+           }
+        }
+     }
+#endif /* PNG_READ_BACKGROUND_SUPPORTED || PNG_RGB_TO_GRAY_SUPPORTED */
+  }
+}
+#endif
+/* To do: install integer version of png_build_gamma_table here */
+#endif
 
 #ifdef PNG_MNG_FEATURES_SUPPORTED
 /* Undoes intrapixel differencing  */
 void /* PRIVATE */
 png_do_read_intrapixel(png_row_infop row_info, png_bytep row)
 {
    png_debug(1, "in png_do_read_intrapixel");
 
    if (
+#ifdef PNG_USELESS_TESTS_SUPPORTED
+       row != NULL && row_info != NULL &&
+#endif
        (row_info->color_type & PNG_COLOR_MASK_COLOR))
    {
       int bytes_per_pixel;
       png_uint_32 row_width = row_info->width;
-
       if (row_info->bit_depth == 8)
       {
          png_bytep rp;
          png_uint_32 i;
 
          if (row_info->color_type == PNG_COLOR_TYPE_RGB)
             bytes_per_pixel = 3;
 
          else if (row_info->color_type == PNG_COLOR_TYPE_RGB_ALPHA)
             bytes_per_pixel = 4;
 
          else
             return;
 
          for (i = 0, rp = row; i < row_width; i++, rp += bytes_per_pixel)
          {
-            *(rp) = (png_byte)((256 + *rp + *(rp + 1)) & 0xff);
-            *(rp+2) = (png_byte)((256 + *(rp + 2) + *(rp + 1)) & 0xff);
+            *(rp) = (png_byte)((256 + *rp + *(rp+1))&0xff);
+            *(rp+2) = (png_byte)((256 + *(rp+2) + *(rp+1))&0xff);
          }
       }
       else if (row_info->bit_depth == 16)
       {
          png_bytep rp;
          png_uint_32 i;
 
          if (row_info->color_type == PNG_COLOR_TYPE_RGB)
             bytes_per_pixel = 6;
 
          else if (row_info->color_type == PNG_COLOR_TYPE_RGB_ALPHA)
             bytes_per_pixel = 8;
 
          else
             return;
 
          for (i = 0, rp = row; i < row_width; i++, rp += bytes_per_pixel)
          {
             png_uint_32 s0   = (*(rp    ) << 8) | *(rp + 1);
             png_uint_32 s1   = (*(rp + 2) << 8) | *(rp + 3);
             png_uint_32 s2   = (*(rp + 4) << 8) | *(rp + 5);
-            png_uint_32 red  = (s0 + s1 + 65536) & 0xffff;
-            png_uint_32 blue = (s2 + s1 + 65536) & 0xffff;
-            *(rp    ) = (png_byte)((red >> 8) & 0xff);
-            *(rp + 1) = (png_byte)(red & 0xff);
-            *(rp + 4) = (png_byte)((blue >> 8) & 0xff);
-            *(rp + 5) = (png_byte)(blue & 0xff);
+            png_uint_32 red  = (png_uint_32)((s0 + s1 + 65536L) & 0xffffL);
+            png_uint_32 blue = (png_uint_32)((s2 + s1 + 65536L) & 0xffffL);
+            *(rp  ) = (png_byte)((red >> 8) & 0xff);
+            *(rp+1) = (png_byte)(red & 0xff);
+            *(rp+4) = (png_byte)((blue >> 8) & 0xff);
+            *(rp+5) = (png_byte)(blue & 0xff);
          }
       }
    }
 }
 #endif /* PNG_MNG_FEATURES_SUPPORTED */
 #endif /* PNG_READ_SUPPORTED */