Updates the PNG library to 1.2.37, enables some functionality for O3D

third_party/libpng/pngrtran.c

 
 /* pngrtran.c - transforms the data in a row for PNG readers
  *
- * Last changed in libpng 1.2.35 [February 14, 2009]
+ * Last changed in libpng 1.2.37 [June 4, 2009]
  * For conditions of distribution and use, see copyright notice in png.h
  * Copyright (c) 1998-2009 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 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.
  */
 
 #define PNG_INTERNAL
 #include "png.h"
 #if defined(PNG_READ_SUPPORTED)
 
 /* Set the action on getting a CRC error for an ancillary or critical chunk. */
 void PNGAPI
 png_set_crc_action(png_structp png_ptr, int crit_action, int ancil_action)
 {
    png_debug(1, "in png_set_crc_action");
    /* Tell libpng how we react to CRC errors in critical chunks */
-   if (png_ptr == NULL) return;
+   if (png_ptr == NULL)
+      return;
    switch (crit_action)
    {
-      case PNG_CRC_NO_CHANGE:                        /* leave setting as is */
+      case PNG_CRC_NO_CHANGE:                        /* Leave setting as is */
          break;
-      case PNG_CRC_WARN_USE:                               /* warn/use data */
+
+      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 */
+
+      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 */
+
+      case PNG_CRC_WARN_DISCARD:    /* Not a valid action for critical data */
          png_warning(png_ptr,
             "Can't discard critical data on CRC error.");
-      case PNG_CRC_ERROR_QUIT:                                /* error/quit */
+      case PNG_CRC_ERROR_QUIT:                                /* Error/quit */
+
       case PNG_CRC_DEFAULT:
       default:
          png_ptr->flags &= ~PNG_FLAG_CRC_CRITICAL_MASK;
          break;
    }
 
    switch (ancil_action)
    {
-      case PNG_CRC_NO_CHANGE:                       /* leave setting as is */
+      case PNG_CRC_NO_CHANGE:                       /* Leave setting as is */
          break;
-      case PNG_CRC_WARN_USE:                              /* warn/use data */
+
+      case PNG_CRC_WARN_USE:                              /* Warn/use data */
          png_ptr->flags &= ~PNG_FLAG_CRC_ANCILLARY_MASK;
          png_ptr->flags |= PNG_FLAG_CRC_ANCILLARY_USE;
          break;
-      case PNG_CRC_QUIET_USE:                            /* quiet/use data */
+
+      case PNG_CRC_QUIET_USE:                            /* Quiet/use data */
          png_ptr->flags &= ~PNG_FLAG_CRC_ANCILLARY_MASK;
          png_ptr->flags |= PNG_FLAG_CRC_ANCILLARY_USE |
                            PNG_FLAG_CRC_ANCILLARY_NOWARN;
          break;
-      case PNG_CRC_ERROR_QUIT:                               /* error/quit */
+
+      case PNG_CRC_ERROR_QUIT:                               /* Error/quit */
          png_ptr->flags &= ~PNG_FLAG_CRC_ANCILLARY_MASK;
          png_ptr->flags |= PNG_FLAG_CRC_ANCILLARY_NOWARN;
          break;
-      case PNG_CRC_WARN_DISCARD:                      /* warn/discard data */
+
+      case PNG_CRC_WARN_DISCARD:                      /* Warn/discard data */
+
       case PNG_CRC_DEFAULT:
       default:
          png_ptr->flags &= ~PNG_FLAG_CRC_ANCILLARY_MASK;
          break;
    }
 }
 
 #if defined(PNG_READ_BACKGROUND_SUPPORTED) && \
     defined(PNG_FLOATING_POINT_SUPPORTED)
-/* handle alpha and tRNS via a background color */
+/* 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)
 {
    png_debug(1, "in png_set_background");
-   if (png_ptr == NULL) return;
+   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_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);
    png_ptr->transformations |= (need_expand ? PNG_BACKGROUND_EXPAND : 0);
 }
 #endif
 
 #if defined(PNG_READ_16_TO_8_SUPPORTED)
-/* strip 16 bit depth files to 8 bit depth */
+/* Strip 16 bit depth files to 8 bit depth */
 void PNGAPI
 png_set_strip_16(png_structp png_ptr)
 {
    png_debug(1, "in png_set_strip_16");
-   if (png_ptr == NULL) return;
+   if (png_ptr == NULL)
+      return;
    png_ptr->transformations |= PNG_16_TO_8;
 }
 #endif
 
 #if defined(PNG_READ_STRIP_ALPHA_SUPPORTED)
 void PNGAPI
 png_set_strip_alpha(png_structp png_ptr)
 {
    png_debug(1, "in png_set_strip_alpha");
-   if (png_ptr == NULL) return;
+   if (png_ptr == NULL)
+      return;
    png_ptr->flags |= PNG_FLAG_STRIP_ALPHA;
 }
 #endif
 
 #if defined(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_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 FAR * next;
    png_byte left;
    png_byte right;
 } png_dsort;
 typedef png_dsort FAR *       png_dsortp;
 typedef png_dsort FAR * FAR * png_dsortpp;
 
 void PNGAPI
 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_dither");
-   if (png_ptr == NULL) return;
+   if (png_ptr == NULL)
+      return;
    png_ptr->transformations |= PNG_DITHER;
 
    if (!full_dither)
    {
       int i;
 
       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->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. */
+          * Perhaps not the best solution, but good enough.
+          */
 
          int i;
 
-         /* initialize an array to sort colors */
+         /* Initialize an array to sort colors */
          png_ptr->dither_sort = (png_bytep)png_malloc(png_ptr,
             (png_uint_32)(num_palette * png_sizeof(png_byte)));
 
-         /* initialize the dither_sort array */
+         /* Initialize the dither_sort array */
          for (i = 0; i < num_palette; 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. */
+          * 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 done; /* To stop early if the list is pre-sorted */
             int j;
 
             done = 1;
             for (j = 0; j < i; j++)
             {
                if (histogram[png_ptr->dither_sort[j]]
                    < histogram[png_ptr->dither_sort[j + 1]])
                {
                   png_byte 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 */
+         /* Swap the palette around, and set up a table, if necessary */
          if (full_dither)
          {
             int j = num_palette;
 
-            /* put all the useful colors within the max, but don't
-               move the others */
+            /* 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->dither_sort[i] >= maximum_colors)
                {
                   do
                      j--;
                   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 */
+            /* 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 */
+               /* Only move the colors we need to */
                if ((int)png_ptr->dither_sort[i] >= maximum_colors)
                {
                   png_color tmp_color;
 
                   do
                      j--;
                   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 */
+                  /* Indicate where the color went */
                   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 */
+            /* Find closest color for those colors we are not using */
             for (i = 0; i < num_palette; i++)
             {
                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 */
+                  /* Find the closest color to one we threw out */
                   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 */
+                  /* Point to closest color */
                   png_ptr->dither_index[i] = (png_byte)min_k;
                }
             }
          }
          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]
-            */
+          * 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 */
+         /* Initialize palette index arrays */
          png_ptr->index_to_palette = (png_bytep)png_malloc(png_ptr,
             (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 * png_sizeof(png_byte)));
 
-         /* initialize the sort array */
+         /* 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_malloc(png_ptr, (png_uint_32)(769 *
             png_sizeof(png_dsortp)));
          png_memset(hash, 0, 769 * 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.
-            */
+         /* 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++)
                {
@@ skipping 182 matching lines @@
  * 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");
-   if (png_ptr == NULL) return;
+   if (png_ptr == NULL)
+      return;
    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;
 }
 #endif
 
 #if defined(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_structp png_ptr)
 {
    png_debug(1, "in png_set_expand");
-   if (png_ptr == NULL) return;
+   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-1.4.0, png_set_gray_1_2_4_to_8() was modified
  *  to expand only the sample depth but not to expand the tRNS to alpha.
  */
 
 /* Expand paletted images to RGB. */
 void PNGAPI
 png_set_palette_to_rgb(png_structp png_ptr)
 {
    png_debug(1, "in png_set_palette_to_rgb");
-   if (png_ptr == NULL) return;
+   if (png_ptr == NULL)
+      return;
    png_ptr->transformations |= (PNG_EXPAND | PNG_EXPAND_tRNS);
    png_ptr->flags &= ~PNG_FLAG_ROW_INIT;
 }
 
 #if !defined(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_structp png_ptr)
 {
    png_debug(1, "in png_set_expand_gray_1_2_4_to_8");
-   if (png_ptr == NULL) return;
+   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;
+   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_structp png_ptr)
 {
    png_debug(1, "in png_set_tRNS_to_alpha");
@@ skipping 15 matching lines @@
 #if defined(PNG_READ_RGB_TO_GRAY_SUPPORTED)
 #if defined(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_structp png_ptr, int error_action, double red,
    double green)
 {
-      int red_fixed = (int)((float)red*100000.0 + 0.5);
-      int green_fixed = (int)((float)green*100000.0 + 0.5);
-      if (png_ptr == NULL) return;
-      png_set_rgb_to_gray_fixed(png_ptr, error_action, red_fixed, green_fixed);
+   int red_fixed = (int)((float)red*100000.0 + 0.5);
+   int green_fixed = (int)((float)green*100000.0 + 0.5);
+   if (png_ptr == NULL)
+      return;
+   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");
-   if (png_ptr == NULL) return;
+   if (png_ptr == NULL)
+      return;
    switch(error_action)
    {
       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)
 #if defined(PNG_READ_EXPAND_SUPPORTED)
       png_ptr->transformations |= PNG_EXPAND;
 #else
    {
       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);
+         red_int = (png_uint_16)(((png_uint_32)red*32768L)/100000L);
+         green_int = (png_uint_16)(((png_uint_32)green*32768L)/100000L);
       }
       else
       {
          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_WRITE_USER_TRANSFORM_SUPPORTED) || \
     defined(PNG_LEGACY_SUPPORTED)
 void PNGAPI
 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;
+   if (png_ptr == NULL)
+      return;
 #if defined(PNG_READ_USER_TRANSFORM_SUPPORTED)
    png_ptr->transformations |= PNG_USER_TRANSFORM;
    png_ptr->read_user_transform_fn = read_user_transform_fn;
 #endif
 #ifdef PNG_LEGACY_SUPPORTED
    if (read_user_transform_fn)
       png_warning(png_ptr,
         "This version of libpng does not support user transforms");
 #endif
 }
@@ skipping 12 matching lines @@
   {
 #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)
 
 #if defined(PNG_READ_GRAY_TO_RGB_SUPPORTED)
    /* 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
+    * 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.
     */
    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 */
+         /* Expand background and tRNS chunks */
          switch (png_ptr->bit_depth)
          {
             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;
          }
       }
       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;
 
 #if defined(PNG_READ_INVERT_ALPHA_SUPPORTED)
         if (png_ptr->transformations & PNG_INVERT_ALPHA)
         {
 #if defined(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 */
+           /* 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 */
+        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);
 #if defined(PNG_READ_BACKGROUND_SUPPORTED)
       if (png_ptr->transformations & PNG_BACKGROUND)
       {
          if (color_type == PNG_COLOR_TYPE_PALETTE)
          {
-           /* could skip if no transparency and
-           */
+           /* 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
             {
                double g, gs;
 
                switch (png_ptr->background_gamma_type)
                {
                   case PNG_BACKGROUND_GAMMA_SCREEN:
                      g = (png_ptr->screen_gamma);
                      gs = 1.0;
                      break;
+
                   case PNG_BACKGROUND_GAMMA_FILE:
                      g = 1.0 / (png_ptr->gamma);
                      gs = 1.0 / (png_ptr->gamma * png_ptr->screen_gamma);
                      break;
+
                   case PNG_BACKGROUND_GAMMA_UNIQUE:
                      g = 1.0 / (png_ptr->background_gamma);
                      gs = 1.0 / (png_ptr->background_gamma *
                                  png_ptr->screen_gamma);
                      break;
                   default:
                      g = 1.0;    /* back_1 */
                      gs = 1.0;   /* back */
                }
 
@@ skipping 68 matching lines @@
             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 = 1.0;
                   break;
+
                case PNG_BACKGROUND_GAMMA_FILE:
                   g = 1.0 / (png_ptr->gamma);
                   gs = 1.0 / (png_ptr->gamma * png_ptr->screen_gamma);
                   break;
+
                case PNG_BACKGROUND_GAMMA_UNIQUE:
                   g = 1.0 / (png_ptr->background_gamma);
                   gs = 1.0 / (png_ptr->background_gamma *
                      png_ptr->screen_gamma);
                   break;
             }
 
             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(
@@ skipping 21 matching lines @@
             {
                /* 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.red = png_ptr->background.green
                  = png_ptr->background.blue = png_ptr->background.gray;
             }
          }
       }
       else
-      /* transformation does not include PNG_BACKGROUND */
+      /* Transformation does not include PNG_BACKGROUND */
 #endif /* PNG_READ_BACKGROUND_SUPPORTED */
       if (color_type == PNG_COLOR_TYPE_PALETTE)
       {
          png_colorp palette = png_ptr->palette;
          int num_palette = png_ptr->num_palette;
          int i;
 
          for (i = 0; i < num_palette; i++)
          {
             palette[i].red = png_ptr->gamma_table[palette[i].red];
@@ skipping 151 matching lines @@
 
 #if defined(PNG_READ_RGB_TO_GRAY_SUPPORTED)
    if (png_ptr->transformations & PNG_RGB_TO_GRAY)
       info_ptr->color_type &= ~PNG_COLOR_MASK_COLOR;
 #endif
 
 #if defined(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_RGB_ALPHA)) &&
+          png_ptr->palette_lookup && info_ptr->bit_depth == 8)
       {
          info_ptr->color_type = PNG_COLOR_TYPE_PALETTE;
       }
    }
 #endif
 
 #if defined(PNG_READ_PACK_SUPPORTED)
    if ((png_ptr->transformations & PNG_PACK) && (info_ptr->bit_depth < 8))
       info_ptr->bit_depth = 8;
 #endif
@@ skipping 13 matching lines @@
    if (info_ptr->color_type & PNG_COLOR_MASK_ALPHA)
       info_ptr->channels++;
 
 #if defined(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 */
+      /* If adding a true alpha channel not just filler */
 #if !defined(PNG_1_0_X)
       if (png_ptr->transformations & PNG_ADD_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)
@@ skipping 34 matching lines @@
          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 */
+       * pixels.  This check added to libpng-1.2.19
+       */
 #if (PNG_WARN_UNINITIALIZED_ROW==1)
       png_error(png_ptr, "Uninitialized row");
 #else
       png_warning(png_ptr, "Uninitialized row");
 #endif
 #endif
 
 #if defined(PNG_READ_EXPAND_SUPPORTED)
    if (png_ptr->transformations & PNG_EXPAND)
    {
@@ skipping 32 matching lines @@
          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
-  gray-to-RGB, or you will have to test 3x as many bytes to check if a
-  pixel is transparent.  You would also need to make sure that the
-  transparency information is upgraded to RGB.
-
-  To summarize, the current flow is:
-  - Gray + simple transparency -> compare 1 or 2 gray bytes and composite
-                                  with background "in place" if transparent,
-                                  convert to RGB if necessary
-  - Gray + alpha -> composite with gray background and remove alpha bytes,
-                                  convert to RGB if necessary
-
-  To support RGB backgrounds for gray images we need:
-  - Gray + simple transparency -> convert to RGB + simple transparency, compare
-                                  3 or 6 bytes and composite with background
-                                  "in place" if transparent (3x compare/pixel
-                                  compared to doing composite with gray bkgrnd)
-  - Gray + alpha -> convert to RGB + alpha, composite with background and
-                                  remove alpha bytes (3x float operations/pixel
-                                  compared with composite on gray background)
-
-  Greg's change will do this.  The reason it wasn't done before is for
-  performance, as this increases the per-pixel operations.  If we would check
-  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.
+/* From Andreas Dilger e-mail to png-implement, 26 March 1998:
+ * 
+ *   In most cases, the "simple transparency" should be done prior to doing
+ *   gray-to-RGB, or you will have to test 3x as many bytes to check if a
+ *   pixel is transparent.  You would also need to make sure that the
+ *   transparency information is upgraded to RGB.
+ * 
+ *   To summarize, the current flow is:
+ *   - Gray + simple transparency -> compare 1 or 2 gray bytes and composite
+ *                                   with background "in place" if transparent,
+ *                                   convert to RGB if necessary
+ *   - Gray + alpha -> composite with gray background and remove alpha bytes,
+ *                                   convert to RGB if necessary
+ *
+ *   To support RGB backgrounds for gray images we need:
+ *   - Gray + simple transparency -> convert to RGB + simple transparency,
+ *                                   compare 3 or 6 bytes and composite with
+ *                                   background "in place" if transparent
+ *                                   (3x compare/pixel compared to doing
+ *                                   composite with gray bkgrnd)
+ *   - Gray + alpha -> convert to RGB + alpha, composite with background and
+ *                                   remove alpha bytes (3x float
+ *                                   operations/pixel compared with composite
+ *                                   on gray background)
+ *
+ *  Greg's change will do this.  The reason it wasn't done before is for
+ *  performance, as this increases the per-pixel operations.  If we would check
+ *  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.
  */
 
 #if defined(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 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(&(png_ptr->row_info), png_ptr->row_buf + 1);
 #endif
 
 #if defined(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)
 #if defined(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
 
 #if defined(PNG_READ_GAMMA_SUPPORTED)
    if ((png_ptr->transformations & PNG_GAMMA) &&
 #if defined(PNG_READ_BACKGROUND_SUPPORTED)
-      !((png_ptr->transformations & PNG_BACKGROUND) &&
-      ((png_ptr->num_trans != 0) ||
-      (png_ptr->color_type & PNG_COLOR_MASK_ALPHA))) &&
+       !((png_ptr->transformations & PNG_BACKGROUND) &&
+       ((png_ptr->num_trans != 0) ||
+       (png_ptr->color_type & PNG_COLOR_MASK_ALPHA))) &&
 #endif
-      (png_ptr->color_type != PNG_COLOR_TYPE_PALETTE))
+       (png_ptr->color_type != PNG_COLOR_TYPE_PALETTE))
       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);
+          png_ptr->gamma_table, png_ptr->gamma_16_table,
+          png_ptr->gamma_shift);
 #endif
 
 #if defined(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
 
 #if defined(PNG_READ_DITHER_SUPPORTED)
    if (png_ptr->transformations & PNG_DITHER)
    {
@@ skipping 24 matching lines @@
    if (png_ptr->transformations & PNG_BGR)
       png_do_bgr(&(png_ptr->row_info), png_ptr->row_buf + 1);
 #endif
 
 #if defined(PNG_READ_PACKSWAP_SUPPORTED)
    if (png_ptr->transformations & PNG_PACKSWAP)
       png_do_packswap(&(png_ptr->row_info), png_ptr->row_buf + 1);
 #endif
 
 #if defined(PNG_READ_GRAY_TO_RGB_SUPPORTED)
-   /* if gray -> RGB, do so now only if we did not do so above */
+   /* 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
 
 #if defined(PNG_READ_FILLER_SUPPORTED)
    if (png_ptr->transformations & PNG_FILLER)
       png_do_read_filler(&(png_ptr->row_info), png_ptr->row_buf + 1,
          (png_uint_32)png_ptr->filler, png_ptr->flags);
 #endif
@@ skipping 10 matching lines @@
 
 #if defined(PNG_READ_SWAP_SUPPORTED)
    if (png_ptr->transformations & PNG_SWAP_BYTES)
       png_do_swap(&(png_ptr->row_info), png_ptr->row_buf + 1);
 #endif
 
 #if defined(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 */
-           &(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 */
+         (*(png_ptr->read_user_transform_fn)) /* User read transform function */
+            (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 */
 #if defined(PNG_USER_TRANSFORM_PTR_SUPPORTED)
       if (png_ptr->user_transform_depth)
          png_ptr->row_info.bit_depth = png_ptr->user_transform_depth;
       if (png_ptr->user_transform_channels)
          png_ptr->row_info.channels = png_ptr->user_transform_channels;
 #endif
       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);
@@ skipping 37 matching lines @@
                   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)
                {
@@ skipping 71 matching lines @@
             png_uint_32 i;
             png_uint_32 istop = row_info->rowbytes;
 
             for (bp = row, i = 0; i < istop; i++)
             {
                *bp >>= 1;
                *bp++ &= 0x55;
             }
             break;
          }
+
          case 4:
          {
             png_bytep bp = row;
             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]));
 
             for (i = 0; i < istop; i++)
             {
                *bp >>= shift[0];
                *bp++ &= mask;
             }
             break;
          }
+
          case 8:
          {
             png_bytep bp = row;
             png_uint_32 i;
             png_uint_32 istop = row_width * channels;
 
             for (i = 0; i < istop; i++)
             {
                *bp++ >>= shift[i%channels];
             }
             break;
          }
+
          case 16:
          {
             png_bytep bp = row;
             png_uint_32 i;
             png_uint_32 istop = channels * row_width;
 
             for (i = 0; i < istop; i++)
             {
                value = (png_uint_16)((*bp << 8) + *(bp + 1));
                value >>= shift[i%channels];
                *bp++ = (png_byte)(value >> 8);
                *bp++ = (png_byte)(value & 0xff);
             }
             break;
          }
       }
    }
 }
 #endif
 
 #if defined(PNG_READ_16_TO_8_SUPPORTED)
-/* chop rows of bit depth 16 down to 8 */
+/* Chop rows of bit depth 16 down to 8 */
 void /* PRIVATE */
 png_do_chop(png_row_infop row_info, png_bytep row)
 {
    png_debug(1, "in png_do_chop");
 #if defined(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;
       png_bytep dp = row;
       png_uint_32 i;
       png_uint_32 istop = row_info->width * row_info->channels;
 
       for (i = 0; i<istop; i++, sp += 2, dp++)
       {
 #if defined(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;
+       *          (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;
+       *           (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;
+       *   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);
@@ skipping 369 matching lines @@
             row_info->channels = 4;
             row_info->pixel_depth = 64;
             row_info->rowbytes = row_width * 8;
          }
       }
    } /* COLOR_TYPE == RGB */
 }
 #endif
 
 #if defined(PNG_READ_GRAY_TO_RGB_SUPPORTED)
-/* expand grayscale files to RGB, with or without alpha */
+/* 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 &&
 #if defined(PNG_USELESS_TESTS_SUPPORTED)
        row != NULL && row_info != NULL &&
@@ skipping 62 matching lines @@
       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->rowbytes = PNG_ROWBYTES(row_info->pixel_depth, row_width);
    }
 }
 #endif
 
 #if defined(PNG_READ_RGB_TO_GRAY_SUPPORTED)
-/* reduce RGB files to grayscale, with or without alpha
+/* Reduce RGB files to grayscale, with or without alpha
  * 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
  *
@@ skipping 257 matching lines @@
    png_debug(1, "in png_do_build_grayscale_palette");
    if (palette == NULL)
       return;
 
    switch (bit_depth)
    {
       case 1:
          num_palette = 2;
          color_inc = 0xff;
          break;
+
       case 2:
          num_palette = 4;
          color_inc = 0x55;
          break;
+
       case 4:
          num_palette = 16;
          color_inc = 0x11;
          break;
+
       case 8:
          num_palette = 256;
          color_inc = 1;
          break;
+
       default:
          num_palette = 0;
          color_inc = 0;
          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;
@@ skipping 157 matching lines @@
             {
                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?) */
+      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;
@@ skipping 55 matching lines @@
                      if (!shift)
                      {
                         shift = 7;
                         sp++;
                      }
                      else
                         shift--;
                   }
                   break;
                }
+
                case 2:
                {
 #if defined(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)
@@ skipping 36 matching lines @@
                         {
                            shift = 6;
                            sp++;
                         }
                         else
                            shift -= 2;
                      }
                   }
                   break;
                }
+
                case 4:
                {
 #if defined(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)
@@ skipping 36 matching lines @@
                         {
                            shift = 4;
                            sp++;
                         }
                         else
                            shift -= 4;
                      }
                   }
                   break;
                }
+
                case 8:
                {
 #if defined(PNG_READ_GAMMA_SUPPORTED)
                   if (gamma_table != NULL)
                   {
                      sp = row;
                      for (i = 0; i < row_width; i++, sp++)
                      {
                         if (*sp == trans_values->gray)
                         {
@@ skipping 12 matching lines @@
                      for (i = 0; i < row_width; i++, sp++)
                      {
                         if (*sp == trans_values->gray)
                         {
                            *sp = (png_byte)background->gray;
                         }
                      }
                   }
                   break;
                }
+
                case 16:
                {
 #if defined(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 == trans_values->gray)
                         {
-                           /* background is already in screen gamma */
+                           /* Background is already in screen gamma */
                            *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);
                         }
                      }
@@ skipping 12 matching lines @@
                            *sp = (png_byte)((background->gray >> 8) & 0xff);
                            *(sp + 1) = (png_byte)(background->gray & 0xff);
                         }
                      }
                   }
                   break;
                }
             }
             break;
          }
+
          case PNG_COLOR_TYPE_RGB:
          {
             if (row_info->bit_depth == 8)
             {
 #if defined(PNG_READ_GAMMA_SUPPORTED)
                if (gamma_table != NULL)
                {
                   sp = row;
                   for (i = 0; i < row_width; i++, sp += 3)
                   {
@@ skipping 37 matching lines @@
                {
                   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 == trans_values->red && g == trans_values->green &&
                         b == trans_values->blue)
                      {
-                        /* background is already in screen gamma */
+                        /* Background is already in screen gamma */
                         *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];
@@ skipping 26 matching lines @@
                         *(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)
             {
 #if defined(PNG_READ_GAMMA_SUPPORTED)
                if (gamma_to_1 != NULL && gamma_from_1 != NULL &&
                    gamma_table != NULL)
                {
                   sp = row;
                   dp = row;
                   for (i = 0; i < row_width; i++, sp += 2, dp++)
                   {
                      png_uint_16 a = *(sp + 1);
 
                      if (a == 0xff)
                      {
                         *dp = gamma_table[*sp];
                      }
                      else if (a == 0)
                      {
-                        /* background is already in screen gamma */
+                        /* Background is already in screen gamma */
                         *dp = (png_byte)background->gray;
                      }
                      else
                      {
                         png_byte v, w;
 
                         v = gamma_to_1[*sp];
                         png_composite(w, v, a, background_1->gray);
                         *dp = gamma_from_1[w];
                      }
@@ skipping 46 matching lines @@
                         v = gamma_16[*(sp + 1) >> gamma_shift][*sp];
                         *dp = (png_byte)((v >> 8) & 0xff);
                         *(dp + 1) = (png_byte)(v & 0xff);
                      }
 #if defined(PNG_READ_GAMMA_SUPPORTED)
                      else if (a == 0)
 #else
                      else
 #endif
                      {
-                        /* background is already in screen gamma */
+                        /* Background is already in screen gamma */
                         *dp = (png_byte)((background->gray >> 8) & 0xff);
                         *(dp + 1) = (png_byte)(background->gray & 0xff);
                      }
 #if defined(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, background_1->gray);
@@ skipping 34 matching lines @@
                         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)
             {
 #if defined(PNG_READ_GAMMA_SUPPORTED)
                if (gamma_to_1 != NULL && gamma_from_1 != NULL &&
                    gamma_table != NULL)
                {
                   sp = row;
                   dp = row;
                   for (i = 0; i < row_width; i++, sp += 4, dp += 3)
                   {
                      png_byte a = *(sp + 3);
 
                      if (a == 0xff)
                      {
                         *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 */
+                        /* Background is already in screen gamma */
                         *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, background_1->red);
@@ skipping 60 matching lines @@
                         *(dp + 1) = (png_byte)(v & 0xff);
                         v = gamma_16[*(sp + 3) >> gamma_shift][*(sp + 2)];
                         *(dp + 2) = (png_byte)((v >> 8) & 0xff);
                         *(dp + 3) = (png_byte)(v & 0xff);
                         v = gamma_16[*(sp + 5) >> gamma_shift][*(sp + 4)];
                         *(dp + 4) = (png_byte)((v >> 8) & 0xff);
                         *(dp + 5) = (png_byte)(v & 0xff);
                      }
                      else if (a == 0)
                      {
-                        /* background is already in screen gamma */
+                        /* Background is already in screen gamma */
                         *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, x;
@@ skipping 134 matching lines @@
                   *(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];
@@ skipping 17 matching lines @@
                   *(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;
                }
             }
             break;
          }
+
          case PNG_COLOR_TYPE_GRAY:
          {
             if (row_info->bit_depth == 2)
             {
                sp = row;
                for (i = 0; i < row_width; i += 4)
                {
                   int a = *sp & 0xc0;
                   int b = *sp & 0x30;
                   int c = *sp & 0x0c;
                   int d = *sp & 0x03;
 
                   *sp = (png_byte)(
                         ((((int)gamma_table[a|(a>>2)|(a>>4)|(a>>6)])   ) & 0xc0)|
                         ((((int)gamma_table[(b<<2)|b|(b>>2)|(b>>4)])>>2) & 0x30)|
                         ((((int)gamma_table[(c<<4)|(c<<2)|c|(c>>2)])>>4) & 0x0c)|
                         ((((int)gamma_table[(d<<6)|(d<<4)|(d<<2)|d])>>6) ));
                   sp++;
                }
             }
+
             if (row_info->bit_depth == 4)
             {
                sp = row;
                for (i = 0; i < row_width; i += 2)
                {
                   int msb = *sp & 0xf0;
                   int lsb = *sp & 0x0f;
 
                   *sp = (png_byte)((((int)gamma_table[msb | (msb >> 4)]) & 0xf0)
                           | (((int)gamma_table[(lsb << 4) | lsb]) >> 4));
                   sp++;
                }
             }
+
             else if (row_info->bit_depth == 8)
             {
                sp = row;
                for (i = 0; i < row_width; i++)
                {
                   *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 = gamma_16_table[*(sp + 1) >> gamma_shift][*sp];
                   *sp = (png_byte)((v >> 8) & 0xff);
                   *(sp + 1) = (png_byte)(v & 0xff);
                   sp += 2;
                }
@@ skipping 45 matching lines @@
                      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)
@@ skipping 44 matching lines @@
                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;
          }
       }
    }
@@ skipping 41 matching lines @@
                         shift = 0;
                         sp--;
                      }
                      else
                         shift++;
 
                      dp--;
                   }
                   break;
                }
+
                case 2:
                {
                   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 = (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;
                }
             }
+
             row_info->bit_depth = 8;
             row_info->pixel_depth = 8;
             row_info->rowbytes = row_width;
          }
 
          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)
             {
                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_value)
       {
          if (row_info->bit_depth == 8)
@@ skipping 77 matching lines @@
       {
          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);
-               */
+            /* 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_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];
@@ skipping 60 matching lines @@
 {
   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);
@@ skipping 14 matching lines @@
            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 */
+           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
@@ skipping 37 matching lines @@
         }
      }
      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) || \
@@ skipping 17 matching lines @@
            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 */
+           g = png_ptr->gamma;   /* Probably doing rgb_to_gray */
 
         png_ptr->gamma_16_from_1 = (png_uint_16pp)png_malloc(png_ptr,
            (png_uint_32)(num * png_sizeof(png_uint_16p)));
         png_memset(png_ptr->gamma_16_from_1, 0,
            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
 
 #if defined(PNG_MNG_FEATURES_SUPPORTED)
-/* undoes intrapixel differencing  */
+/* 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 (
 #if defined(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);
          }
       }
       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  = (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 */