XFA: Upgrade libpng to 1.6.20.

third_party/lpng_v163/pngwrite.c

-
-/* pngwrite.c - general routines to write a PNG file
- *
- * Last changed in libpng 1.6.2 [April 25, 2013]
- * Copyright (c) 1998-2013 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
- */
-#include "pngpriv.h"
-#if defined(PNG_SIMPLIFIED_WRITE_SUPPORTED) && defined(PNG_STDIO_SUPPORTED)
-#  include <errno.h>
-#endif
-
-#ifdef PNG_WRITE_SUPPORTED
-
-#ifdef PNG_WRITE_UNKNOWN_CHUNKS_SUPPORTED
-/* Write out all the unknown chunks for the current given location */
-static void
-write_unknown_chunks(png_structrp png_ptr, png_const_inforp info_ptr,
-   unsigned int where)
-{
-   if (info_ptr->unknown_chunks_num)
-   {
-      png_const_unknown_chunkp up;
-
-      png_debug(5, "writing extra chunks");
-
-      for (up = info_ptr->unknown_chunks;
-           up < info_ptr->unknown_chunks + info_ptr->unknown_chunks_num;
-           ++up)
-         if (up->location & where)
-      {
-         /* If per-chunk unknown chunk handling is enabled use it, otherwise
-          * just write the chunks the application has set.
-          */
-#ifdef PNG_SET_UNKNOWN_CHUNKS_SUPPORTED
-         int keep = png_handle_as_unknown(png_ptr, up->name);
-
-         /* NOTE: this code is radically different from the read side in the
-          * matter of handling an ancillary unknown chunk.  In the read side
-          * the default behavior is to discard it, in the code below the default
-          * behavior is to write it.  Critical chunks are, however, only
-          * written if explicitly listed or if the default is set to write all
-          * unknown chunks.
-          *
-          * The default handling is also slightly weird - it is not possible to
-          * stop the writing of all unsafe-to-copy chunks!
-          *
-          * TODO: REVIEW: this would seem to be a bug.
-          */
-         if (keep != PNG_HANDLE_CHUNK_NEVER &&
-             ((up->name[3] & 0x20) /* safe-to-copy overrides everything */ ||
-              keep == PNG_HANDLE_CHUNK_ALWAYS ||
-              (keep == PNG_HANDLE_CHUNK_AS_DEFAULT &&
-               png_ptr->unknown_default == PNG_HANDLE_CHUNK_ALWAYS)))
-#endif
-         {
-            /* TODO: review, what is wrong with a zero length unknown chunk? */
-            if (up->size == 0)
-               png_warning(png_ptr, "Writing zero-length unknown chunk");
-
-            png_write_chunk(png_ptr, up->name, up->data, up->size);
-         }
-      }
-   }
-}
-#endif /* PNG_WRITE_UNKNOWN_CHUNKS_SUPPORTED */
-
-/* Writes all the PNG information.  This is the suggested way to use the
- * library.  If you have a new chunk to add, make a function to write it,
- * and put it in the correct location here.  If you want the chunk written
- * after the image data, put it in png_write_end().  I strongly encourage
- * you to supply a PNG_INFO_ flag, and check info_ptr->valid before writing
- * the chunk, as that will keep the code from breaking if you want to just
- * write a plain PNG file.  If you have long comments, I suggest writing
- * them in png_write_end(), and compressing them.
- */
-void PNGAPI
-png_write_info_before_PLTE(png_structrp png_ptr, png_const_inforp info_ptr)
-{
-   png_debug(1, "in png_write_info_before_PLTE");
-
-   if (png_ptr == NULL || info_ptr == NULL)
-      return;
-
-   if (!(png_ptr->mode & PNG_WROTE_INFO_BEFORE_PLTE))
-   {
-   /* Write PNG signature */
-   png_write_sig(png_ptr);
-
-#ifdef PNG_MNG_FEATURES_SUPPORTED
-   if ((png_ptr->mode&PNG_HAVE_PNG_SIGNATURE) && \
-       (png_ptr->mng_features_permitted))
-   {
-      png_warning(png_ptr, "MNG features are not allowed in a PNG datastream");
-      png_ptr->mng_features_permitted = 0;
-   }
-#endif
-
-   /* Write IHDR information. */
-   png_write_IHDR(png_ptr, info_ptr->width, info_ptr->height,
-       info_ptr->bit_depth, info_ptr->color_type, info_ptr->compression_type,
-       info_ptr->filter_type,
-#ifdef PNG_WRITE_INTERLACING_SUPPORTED
-       info_ptr->interlace_type
-#else
-       0
-#endif
-      );
-
-   /* The rest of these check to see if the valid field has the appropriate
-    * flag set, and if it does, writes the chunk.
-    *
-    * 1.6.0: COLORSPACE support controls the writing of these chunks too, and
-    * the chunks will be written if the WRITE routine is there and information
-    * is available in the COLORSPACE.  (See png_colorspace_sync_info in png.c
-    * for where the valid flags get set.)
-    *
-    * Under certain circumstances the colorspace can be invalidated without
-    * syncing the info_struct 'valid' flags; this happens if libpng detects and
-    * error and calls png_error while the color space is being set, yet the
-    * application continues writing the PNG.  So check the 'invalid' flag here
-    * too.
-    */
-#ifdef PNG_GAMMA_SUPPORTED
-#  ifdef PNG_WRITE_gAMA_SUPPORTED
-      if (!(info_ptr->colorspace.flags & PNG_COLORSPACE_INVALID) &&
-         (info_ptr->colorspace.flags & PNG_COLORSPACE_FROM_gAMA) &&
-         (info_ptr->valid & PNG_INFO_gAMA))
-         png_write_gAMA_fixed(png_ptr, info_ptr->colorspace.gamma);
-#  endif
-#endif
-
-#ifdef PNG_COLORSPACE_SUPPORTED
-   /* Write only one of sRGB or an ICC profile.  If a profile was supplied
-    * and it matches one of the known sRGB ones issue a warning.
-    */
-#  ifdef PNG_WRITE_iCCP_SUPPORTED
-      if (!(info_ptr->colorspace.flags & PNG_COLORSPACE_INVALID) &&
-         (info_ptr->valid & PNG_INFO_iCCP))
-      {
-#        ifdef PNG_WRITE_sRGB_SUPPORTED
-            if (info_ptr->valid & PNG_INFO_sRGB)
-               png_app_warning(png_ptr,
-                  "profile matches sRGB but writing iCCP instead");
-#        endif
-
-         png_write_iCCP(png_ptr, info_ptr->iccp_name,
-            info_ptr->iccp_profile);
-      }
-#     ifdef PNG_WRITE_sRGB_SUPPORTED
-         else
-#     endif
-#  endif
-
-#  ifdef PNG_WRITE_sRGB_SUPPORTED
-      if (!(info_ptr->colorspace.flags & PNG_COLORSPACE_INVALID) &&
-         (info_ptr->valid & PNG_INFO_sRGB))
-         png_write_sRGB(png_ptr, info_ptr->colorspace.rendering_intent);
-#  endif /* WRITE_sRGB */
-#endif /* COLORSPACE */
-
-#ifdef PNG_WRITE_sBIT_SUPPORTED
-   if (info_ptr->valid & PNG_INFO_sBIT)
-      png_write_sBIT(png_ptr, &(info_ptr->sig_bit), info_ptr->color_type);
-#endif
-
-#ifdef PNG_COLORSPACE_SUPPORTED
-#  ifdef PNG_WRITE_cHRM_SUPPORTED
-      if (!(info_ptr->colorspace.flags & PNG_COLORSPACE_INVALID) &&
-         (info_ptr->colorspace.flags & PNG_COLORSPACE_FROM_cHRM) &&
-         (info_ptr->valid & PNG_INFO_cHRM))
-         png_write_cHRM_fixed(png_ptr, &info_ptr->colorspace.end_points_xy);
-#  endif
-#endif
-
-#ifdef PNG_WRITE_UNKNOWN_CHUNKS_SUPPORTED
-      write_unknown_chunks(png_ptr, info_ptr, PNG_HAVE_IHDR);
-#endif
-
-      png_ptr->mode |= PNG_WROTE_INFO_BEFORE_PLTE;
-   }
-}
-
-void PNGAPI
-png_write_info(png_structrp png_ptr, png_const_inforp info_ptr)
-{
-#if defined(PNG_WRITE_TEXT_SUPPORTED) || defined(PNG_WRITE_sPLT_SUPPORTED)
-   int i;
-#endif
-
-   png_debug(1, "in png_write_info");
-
-   if (png_ptr == NULL || info_ptr == NULL)
-      return;
-
-   png_write_info_before_PLTE(png_ptr, info_ptr);
-
-   if (info_ptr->valid & PNG_INFO_PLTE)
-      png_write_PLTE(png_ptr, info_ptr->palette,
-          (png_uint_32)info_ptr->num_palette);
-
-   else if (info_ptr->color_type == PNG_COLOR_TYPE_PALETTE)
-      png_error(png_ptr, "Valid palette required for paletted images");
-
-#ifdef PNG_WRITE_tRNS_SUPPORTED
-   if (info_ptr->valid & PNG_INFO_tRNS)
-   {
-#ifdef PNG_WRITE_INVERT_ALPHA_SUPPORTED
-      /* Invert the alpha channel (in tRNS) */
-      if ((png_ptr->transformations & PNG_INVERT_ALPHA) &&
-          info_ptr->color_type == PNG_COLOR_TYPE_PALETTE)
-      {
-         int j;
-         for (j = 0; j<(int)info_ptr->num_trans; j++)
-            info_ptr->trans_alpha[j] =
-               (png_byte)(255 - info_ptr->trans_alpha[j]);
-      }
-#endif
-      png_write_tRNS(png_ptr, info_ptr->trans_alpha, &(info_ptr->trans_color),
-          info_ptr->num_trans, info_ptr->color_type);
-   }
-#endif
-#ifdef PNG_WRITE_bKGD_SUPPORTED
-   if (info_ptr->valid & PNG_INFO_bKGD)
-      png_write_bKGD(png_ptr, &(info_ptr->background), info_ptr->color_type);
-#endif
-
-#ifdef PNG_WRITE_hIST_SUPPORTED
-   if (info_ptr->valid & PNG_INFO_hIST)
-      png_write_hIST(png_ptr, info_ptr->hist, info_ptr->num_palette);
-#endif
-
-#ifdef PNG_WRITE_oFFs_SUPPORTED
-   if (info_ptr->valid & PNG_INFO_oFFs)
-      png_write_oFFs(png_ptr, info_ptr->x_offset, info_ptr->y_offset,
-          info_ptr->offset_unit_type);
-#endif
-
-#ifdef PNG_WRITE_pCAL_SUPPORTED
-   if (info_ptr->valid & PNG_INFO_pCAL)
-      png_write_pCAL(png_ptr, info_ptr->pcal_purpose, info_ptr->pcal_X0,
-          info_ptr->pcal_X1, info_ptr->pcal_type, info_ptr->pcal_nparams,
-          info_ptr->pcal_units, info_ptr->pcal_params);
-#endif
-
-#ifdef PNG_WRITE_sCAL_SUPPORTED
-   if (info_ptr->valid & PNG_INFO_sCAL)
-      png_write_sCAL_s(png_ptr, (int)info_ptr->scal_unit,
-          info_ptr->scal_s_width, info_ptr->scal_s_height);
-#endif /* sCAL */
-
-#ifdef PNG_WRITE_pHYs_SUPPORTED
-   if (info_ptr->valid & PNG_INFO_pHYs)
-      png_write_pHYs(png_ptr, info_ptr->x_pixels_per_unit,
-          info_ptr->y_pixels_per_unit, info_ptr->phys_unit_type);
-#endif /* pHYs */
-
-#ifdef PNG_WRITE_tIME_SUPPORTED
-   if (info_ptr->valid & PNG_INFO_tIME)
-   {
-      png_write_tIME(png_ptr, &(info_ptr->mod_time));
-      png_ptr->mode |= PNG_WROTE_tIME;
-   }
-#endif /* tIME */
-
-#ifdef PNG_WRITE_sPLT_SUPPORTED
-   if (info_ptr->valid & PNG_INFO_sPLT)
-      for (i = 0; i < (int)info_ptr->splt_palettes_num; i++)
-         png_write_sPLT(png_ptr, info_ptr->splt_palettes + i);
-#endif /* sPLT */
-
-#ifdef PNG_WRITE_TEXT_SUPPORTED
-   /* Check to see if we need to write text chunks */
-   for (i = 0; i < info_ptr->num_text; i++)
-   {
-      png_debug2(2, "Writing header text chunk %d, type %d", i,
-          info_ptr->text[i].compression);
-      /* An internationalized chunk? */
-      if (info_ptr->text[i].compression > 0)
-      {
-#ifdef PNG_WRITE_iTXt_SUPPORTED
-         /* Write international chunk */
-         png_write_iTXt(png_ptr,
-             info_ptr->text[i].compression,
-             info_ptr->text[i].key,
-             info_ptr->text[i].lang,
-             info_ptr->text[i].lang_key,
-             info_ptr->text[i].text);
-#else
-          png_warning(png_ptr, "Unable to write international text");
-#endif
-          /* Mark this chunk as written */
-          info_ptr->text[i].compression = PNG_TEXT_COMPRESSION_NONE_WR;
-      }
-
-      /* If we want a compressed text chunk */
-      else if (info_ptr->text[i].compression == PNG_TEXT_COMPRESSION_zTXt)
-      {
-#ifdef PNG_WRITE_zTXt_SUPPORTED
-         /* Write compressed chunk */
-         png_write_zTXt(png_ptr, info_ptr->text[i].key,
-             info_ptr->text[i].text, 0,
-             info_ptr->text[i].compression);
-#else
-         png_warning(png_ptr, "Unable to write compressed text");
-#endif
-         /* Mark this chunk as written */
-         info_ptr->text[i].compression = PNG_TEXT_COMPRESSION_zTXt_WR;
-      }
-
-      else if (info_ptr->text[i].compression == PNG_TEXT_COMPRESSION_NONE)
-      {
-#ifdef PNG_WRITE_tEXt_SUPPORTED
-         /* Write uncompressed chunk */
-         png_write_tEXt(png_ptr, info_ptr->text[i].key,
-             info_ptr->text[i].text,
-             0);
-         /* Mark this chunk as written */
-         info_ptr->text[i].compression = PNG_TEXT_COMPRESSION_NONE_WR;
-#else
-         /* Can't get here */
-         png_warning(png_ptr, "Unable to write uncompressed text");
-#endif
-      }
-   }
-#endif /* tEXt */
-
-#ifdef PNG_WRITE_UNKNOWN_CHUNKS_SUPPORTED
-   write_unknown_chunks(png_ptr, info_ptr, PNG_HAVE_PLTE);
-#endif
-}
-
-/* Writes the end of the PNG file.  If you don't want to write comments or
- * time information, you can pass NULL for info.  If you already wrote these
- * in png_write_info(), do not write them again here.  If you have long
- * comments, I suggest writing them here, and compressing them.
- */
-void PNGAPI
-png_write_end(png_structrp png_ptr, png_inforp info_ptr)
-{
-   png_debug(1, "in png_write_end");
-
-   if (png_ptr == NULL)
-      return;
-
-   if (!(png_ptr->mode & PNG_HAVE_IDAT))
-      png_error(png_ptr, "No IDATs written into file");
-
-#ifdef PNG_WRITE_CHECK_FOR_INVALID_INDEX_SUPPORTED
-   if (png_ptr->num_palette_max > png_ptr->num_palette)
-      png_benign_error(png_ptr, "Wrote palette index exceeding num_palette");
-#endif
-
-   /* See if user wants us to write information chunks */
-   if (info_ptr != NULL)
-   {
-#ifdef PNG_WRITE_TEXT_SUPPORTED
-      int i; /* local index variable */
-#endif
-#ifdef PNG_WRITE_tIME_SUPPORTED
-      /* Check to see if user has supplied a time chunk */
-      if ((info_ptr->valid & PNG_INFO_tIME) &&
-          !(png_ptr->mode & PNG_WROTE_tIME))
-         png_write_tIME(png_ptr, &(info_ptr->mod_time));
-
-#endif
-#ifdef PNG_WRITE_TEXT_SUPPORTED
-      /* Loop through comment chunks */
-      for (i = 0; i < info_ptr->num_text; i++)
-      {
-         png_debug2(2, "Writing trailer text chunk %d, type %d", i,
-            info_ptr->text[i].compression);
-         /* An internationalized chunk? */
-         if (info_ptr->text[i].compression > 0)
-         {
-#ifdef PNG_WRITE_iTXt_SUPPORTED
-            /* Write international chunk */
-            png_write_iTXt(png_ptr,
-                info_ptr->text[i].compression,
-                info_ptr->text[i].key,
-                info_ptr->text[i].lang,
-                info_ptr->text[i].lang_key,
-                info_ptr->text[i].text);
-#else
-            png_warning(png_ptr, "Unable to write international text");
-#endif
-            /* Mark this chunk as written */
-            info_ptr->text[i].compression = PNG_TEXT_COMPRESSION_NONE_WR;
-         }
-
-         else if (info_ptr->text[i].compression >= PNG_TEXT_COMPRESSION_zTXt)
-         {
-#ifdef PNG_WRITE_zTXt_SUPPORTED
-            /* Write compressed chunk */
-            png_write_zTXt(png_ptr, info_ptr->text[i].key,
-                info_ptr->text[i].text, 0,
-                info_ptr->text[i].compression);
-#else
-            png_warning(png_ptr, "Unable to write compressed text");
-#endif
-            /* Mark this chunk as written */
-            info_ptr->text[i].compression = PNG_TEXT_COMPRESSION_zTXt_WR;
-         }
-
-         else if (info_ptr->text[i].compression == PNG_TEXT_COMPRESSION_NONE)
-         {
-#ifdef PNG_WRITE_tEXt_SUPPORTED
-            /* Write uncompressed chunk */
-            png_write_tEXt(png_ptr, info_ptr->text[i].key,
-                info_ptr->text[i].text, 0);
-#else
-            png_warning(png_ptr, "Unable to write uncompressed text");
-#endif
-
-            /* Mark this chunk as written */
-            info_ptr->text[i].compression = PNG_TEXT_COMPRESSION_NONE_WR;
-         }
-      }
-#endif
-#ifdef PNG_WRITE_UNKNOWN_CHUNKS_SUPPORTED
-      write_unknown_chunks(png_ptr, info_ptr, PNG_AFTER_IDAT);
-#endif
-   }
-
-   png_ptr->mode |= PNG_AFTER_IDAT;
-
-   /* Write end of PNG file */
-   png_write_IEND(png_ptr);
-   /* This flush, added in libpng-1.0.8, removed from libpng-1.0.9beta03,
-    * and restored again in libpng-1.2.30, may cause some applications that
-    * do not set png_ptr->output_flush_fn to crash.  If your application
-    * experiences a problem, please try building libpng with
-    * PNG_WRITE_FLUSH_AFTER_IEND_SUPPORTED defined, and report the event to
-    * png-mng-implement at lists.sf.net .
-    */
-#ifdef PNG_WRITE_FLUSH_SUPPORTED
-#  ifdef PNG_WRITE_FLUSH_AFTER_IEND_SUPPORTED
-   png_flush(png_ptr);
-#  endif
-#endif
-}
-
-#ifdef PNG_CONVERT_tIME_SUPPORTED
-void PNGAPI
-png_convert_from_struct_tm(png_timep ptime, PNG_CONST struct tm * ttime)
-{
-   png_debug(1, "in png_convert_from_struct_tm");
-
-   ptime->year = (png_uint_16)(1900 + ttime->tm_year);
-   ptime->month = (png_byte)(ttime->tm_mon + 1);
-   ptime->day = (png_byte)ttime->tm_mday;
-   ptime->hour = (png_byte)ttime->tm_hour;
-   ptime->minute = (png_byte)ttime->tm_min;
-   ptime->second = (png_byte)ttime->tm_sec;
-}
-
-void PNGAPI
-png_convert_from_time_t(png_timep ptime, time_t ttime)
-{
-   struct tm *tbuf;
-
-   png_debug(1, "in png_convert_from_time_t");
-
-   tbuf = gmtime(&ttime);
-   png_convert_from_struct_tm(ptime, tbuf);
-}
-#endif
-
-/* Initialize png_ptr structure, and allocate any memory needed */
-PNG_FUNCTION(png_structp,PNGAPI
-png_create_write_struct,(png_const_charp user_png_ver, png_voidp error_ptr,
-    png_error_ptr error_fn, png_error_ptr warn_fn),PNG_ALLOCATED)
-{
-#ifndef PNG_USER_MEM_SUPPORTED
-   png_structrp png_ptr = png_create_png_struct(user_png_ver, error_ptr,
-      error_fn, warn_fn, NULL, NULL, NULL);
-#else
-   return png_create_write_struct_2(user_png_ver, error_ptr, error_fn,
-       warn_fn, NULL, NULL, NULL);
-}
-
-/* Alternate initialize png_ptr structure, and allocate any memory needed */
-PNG_FUNCTION(png_structp,PNGAPI
-png_create_write_struct_2,(png_const_charp user_png_ver, png_voidp error_ptr,
-    png_error_ptr error_fn, png_error_ptr warn_fn, png_voidp mem_ptr,
-    png_malloc_ptr malloc_fn, png_free_ptr free_fn),PNG_ALLOCATED)
-{
-   png_structrp png_ptr = png_create_png_struct(user_png_ver, error_ptr,
-      error_fn, warn_fn, mem_ptr, malloc_fn, free_fn);
-#endif /* PNG_USER_MEM_SUPPORTED */
-   if (png_ptr != NULL)
-   {
-      /* Set the zlib control values to defaults; they can be overridden by the
-       * application after the struct has been created.
-       */
-      png_ptr->zbuffer_size = PNG_ZBUF_SIZE;
-
-      /* The 'zlib_strategy' setting is irrelevant because png_default_claim in
-       * pngwutil.c defaults it according to whether or not filters will be
-       * used, and ignores this setting.
-       */
-      png_ptr->zlib_strategy = PNG_Z_DEFAULT_STRATEGY;
-      png_ptr->zlib_level = PNG_Z_DEFAULT_COMPRESSION;
-      png_ptr->zlib_mem_level = 8;
-      png_ptr->zlib_window_bits = 15;
-      png_ptr->zlib_method = 8;
-
-#ifdef PNG_WRITE_COMPRESSED_TEXT_SUPPORTED
-      png_ptr->zlib_text_strategy = PNG_TEXT_Z_DEFAULT_STRATEGY;
-      png_ptr->zlib_text_level = PNG_TEXT_Z_DEFAULT_COMPRESSION;
-      png_ptr->zlib_text_mem_level = 8;
-      png_ptr->zlib_text_window_bits = 15;
-      png_ptr->zlib_text_method = 8;
-#endif /* PNG_WRITE_COMPRESSED_TEXT_SUPPORTED */
-
-      /* This is a highly dubious configuration option; by default it is off,
-       * but it may be appropriate for private builds that are testing
-       * extensions not conformant to the current specification, or of
-       * applications that must not fail to write at all costs!
-       */
-#ifdef PNG_BENIGN_WRITE_ERRORS_SUPPORTED
-      png_ptr->flags |= PNG_FLAG_BENIGN_ERRORS_WARN;
-      /* In stable builds only warn if an application error can be completely
-       * handled.
-       */
-#endif
-
-      /* App warnings are warnings in release (or release candidate) builds but
-       * are errors during development.
-       */
-#if PNG_LIBPNG_BUILD_BASE_TYPE >= PNG_LIBPNG_BUILD_RC
-      png_ptr->flags |= PNG_FLAG_APP_WARNINGS_WARN;
-#endif
-
-      /* TODO: delay this, it can be done in png_init_io() (if the app doesn't
-       * do it itself) avoiding setting the default function if it is not
-       * required.
-       */
-      png_set_write_fn(png_ptr, NULL, NULL, NULL);
-   }
-
-   return png_ptr;
-}
-
-
-/* Write a few rows of image data.  If the image is interlaced,
- * either you will have to write the 7 sub images, or, if you
- * have called png_set_interlace_handling(), you will have to
- * "write" the image seven times.
- */
-void PNGAPI
-png_write_rows(png_structrp png_ptr, png_bytepp row,
-    png_uint_32 num_rows)
-{
-   png_uint_32 i; /* row counter */
-   png_bytepp rp; /* row pointer */
-
-   png_debug(1, "in png_write_rows");
-
-   if (png_ptr == NULL)
-      return;
-
-   /* Loop through the rows */
-   for (i = 0, rp = row; i < num_rows; i++, rp++)
-   {
-      png_write_row(png_ptr, *rp);
-   }
-}
-
-/* Write the image.  You only need to call this function once, even
- * if you are writing an interlaced image.
- */
-void PNGAPI
-png_write_image(png_structrp png_ptr, png_bytepp image)
-{
-   png_uint_32 i; /* row index */
-   int pass, num_pass; /* pass variables */
-   png_bytepp rp; /* points to current row */
-
-   if (png_ptr == NULL)
-      return;
-
-   png_debug(1, "in png_write_image");
-
-#ifdef PNG_WRITE_INTERLACING_SUPPORTED
-   /* Initialize interlace handling.  If image is not interlaced,
-    * this will set pass to 1
-    */
-   num_pass = png_set_interlace_handling(png_ptr);
-#else
-   num_pass = 1;
-#endif
-   /* Loop through passes */
-   for (pass = 0; pass < num_pass; pass++)
-   {
-      /* Loop through image */
-      for (i = 0, rp = image; i < png_ptr->height; i++, rp++)
-      {
-         png_write_row(png_ptr, *rp);
-      }
-   }
-}
-
-/* Called by user to write a row of image data */
-void PNGAPI
-png_write_row(png_structrp png_ptr, png_const_bytep row)
-{
-   /* 1.5.6: moved from png_struct to be a local structure: */
-   png_row_info row_info;
-
-   if (png_ptr == NULL)
-      return;
-
-   png_debug2(1, "in png_write_row (row %u, pass %d)",
-      png_ptr->row_number, png_ptr->pass);
-
-   /* Initialize transformations and other stuff if first time */
-   if (png_ptr->row_number == 0 && png_ptr->pass == 0)
-   {
-      /* Make sure we wrote the header info */
-      if (!(png_ptr->mode & PNG_WROTE_INFO_BEFORE_PLTE))
-         png_error(png_ptr,
-             "png_write_info was never called before png_write_row");
-
-      /* Check for transforms that have been set but were defined out */
-#if !defined(PNG_WRITE_INVERT_SUPPORTED) && defined(PNG_READ_INVERT_SUPPORTED)
-      if (png_ptr->transformations & PNG_INVERT_MONO)
-         png_warning(png_ptr, "PNG_WRITE_INVERT_SUPPORTED is not defined");
-#endif
-
-#if !defined(PNG_WRITE_FILLER_SUPPORTED) && defined(PNG_READ_FILLER_SUPPORTED)
-      if (png_ptr->transformations & PNG_FILLER)
-         png_warning(png_ptr, "PNG_WRITE_FILLER_SUPPORTED is not defined");
-#endif
-#if !defined(PNG_WRITE_PACKSWAP_SUPPORTED) && \
-    defined(PNG_READ_PACKSWAP_SUPPORTED)
-      if (png_ptr->transformations & PNG_PACKSWAP)
-         png_warning(png_ptr,
-             "PNG_WRITE_PACKSWAP_SUPPORTED is not defined");
-#endif
-
-#if !defined(PNG_WRITE_PACK_SUPPORTED) && defined(PNG_READ_PACK_SUPPORTED)
-      if (png_ptr->transformations & PNG_PACK)
-         png_warning(png_ptr, "PNG_WRITE_PACK_SUPPORTED is not defined");
-#endif
-
-#if !defined(PNG_WRITE_SHIFT_SUPPORTED) && defined(PNG_READ_SHIFT_SUPPORTED)
-      if (png_ptr->transformations & PNG_SHIFT)
-         png_warning(png_ptr, "PNG_WRITE_SHIFT_SUPPORTED is not defined");
-#endif
-
-#if !defined(PNG_WRITE_BGR_SUPPORTED) && defined(PNG_READ_BGR_SUPPORTED)
-      if (png_ptr->transformations & PNG_BGR)
-         png_warning(png_ptr, "PNG_WRITE_BGR_SUPPORTED is not defined");
-#endif
-
-#if !defined(PNG_WRITE_SWAP_SUPPORTED) && defined(PNG_READ_SWAP_SUPPORTED)
-      if (png_ptr->transformations & PNG_SWAP_BYTES)
-         png_warning(png_ptr, "PNG_WRITE_SWAP_SUPPORTED is not defined");
-#endif
-
-      png_write_start_row(png_ptr);
-   }
-
-#ifdef PNG_WRITE_INTERLACING_SUPPORTED
-   /* If interlaced and not interested in row, return */
-   if (png_ptr->interlaced && (png_ptr->transformations & PNG_INTERLACE))
-   {
-      switch (png_ptr->pass)
-      {
-         case 0:
-            if (png_ptr->row_number & 0x07)
-            {
-               png_write_finish_row(png_ptr);
-               return;
-            }
-            break;
-
-         case 1:
-            if ((png_ptr->row_number & 0x07) || png_ptr->width < 5)
-            {
-               png_write_finish_row(png_ptr);
-               return;
-            }
-            break;
-
-         case 2:
-            if ((png_ptr->row_number & 0x07) != 4)
-            {
-               png_write_finish_row(png_ptr);
-               return;
-            }
-            break;
-
-         case 3:
-            if ((png_ptr->row_number & 0x03) || png_ptr->width < 3)
-            {
-               png_write_finish_row(png_ptr);
-               return;
-            }
-            break;
-
-         case 4:
-            if ((png_ptr->row_number & 0x03) != 2)
-            {
-               png_write_finish_row(png_ptr);
-               return;
-            }
-            break;
-
-         case 5:
-            if ((png_ptr->row_number & 0x01) || png_ptr->width < 2)
-            {
-               png_write_finish_row(png_ptr);
-               return;
-            }
-            break;
-
-         case 6:
-            if (!(png_ptr->row_number & 0x01))
-            {
-               png_write_finish_row(png_ptr);
-               return;
-            }
-            break;
-
-         default: /* error: ignore it */
-            break;
-      }
-   }
-#endif
-
-   /* Set up row info for transformations */
-   row_info.color_type = png_ptr->color_type;
-   row_info.width = png_ptr->usr_width;
-   row_info.channels = png_ptr->usr_channels;
-   row_info.bit_depth = png_ptr->usr_bit_depth;
-   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_debug1(3, "row_info->color_type = %d", row_info.color_type);
-   png_debug1(3, "row_info->width = %u", row_info.width);
-   png_debug1(3, "row_info->channels = %d", row_info.channels);
-   png_debug1(3, "row_info->bit_depth = %d", row_info.bit_depth);
-   png_debug1(3, "row_info->pixel_depth = %d", row_info.pixel_depth);
-   png_debug1(3, "row_info->rowbytes = %lu", (unsigned long)row_info.rowbytes);
-
-   /* Copy user's row into buffer, leaving room for filter byte. */
-   memcpy(png_ptr->row_buf + 1, row, row_info.rowbytes);
-
-#ifdef PNG_WRITE_INTERLACING_SUPPORTED
-   /* Handle interlacing */
-   if (png_ptr->interlaced && png_ptr->pass < 6 &&
-       (png_ptr->transformations & PNG_INTERLACE))
-   {
-      png_do_write_interlace(&row_info, png_ptr->row_buf + 1, png_ptr->pass);
-      /* This should always get caught above, but still ... */
-      if (!(row_info.width))
-      {
-         png_write_finish_row(png_ptr);
-         return;
-      }
-   }
-#endif
-
-#ifdef PNG_WRITE_TRANSFORMS_SUPPORTED
-   /* Handle other transformations */
-   if (png_ptr->transformations)
-      png_do_write_transformations(png_ptr, &row_info);
-#endif
-
-   /* At this point the row_info pixel depth must match the 'transformed' depth,
-    * which is also the output depth.
-    */
-   if (row_info.pixel_depth != png_ptr->pixel_depth ||
-      row_info.pixel_depth != png_ptr->transformed_pixel_depth)
-      png_error(png_ptr, "internal write transform logic error");
-
-#ifdef PNG_MNG_FEATURES_SUPPORTED
-   /* Write filter_method 64 (intrapixel differencing) only if
-    * 1. Libpng was compiled with PNG_MNG_FEATURES_SUPPORTED and
-    * 2. Libpng did not write a PNG signature (this filter_method is only
-    *    used in PNG datastreams that are embedded in MNG datastreams) and
-    * 3. The application called png_permit_mng_features with a mask that
-    *    included PNG_FLAG_MNG_FILTER_64 and
-    * 4. The filter_method is 64 and
-    * 5. The color_type is RGB or RGBA
-    */
-   if ((png_ptr->mng_features_permitted & PNG_FLAG_MNG_FILTER_64) &&
-       (png_ptr->filter_type == PNG_INTRAPIXEL_DIFFERENCING))
-   {
-      /* Intrapixel differencing */
-      png_do_write_intrapixel(&row_info, png_ptr->row_buf + 1);
-   }
-#endif
-
-/* Added at libpng-1.5.10 */
-#ifdef PNG_WRITE_CHECK_FOR_INVALID_INDEX_SUPPORTED
-   /* Check for out-of-range palette index */
-   if (row_info.color_type == PNG_COLOR_TYPE_PALETTE &&
-       png_ptr->num_palette_max >= 0)
-      png_do_check_palette_indexes(png_ptr, &row_info);
-#endif
-
-   /* Find a filter if necessary, filter the row and write it out. */
-   png_write_find_filter(png_ptr, &row_info);
-
-   if (png_ptr->write_row_fn != NULL)
-      (*(png_ptr->write_row_fn))(png_ptr, png_ptr->row_number, png_ptr->pass);
-}
-
-#ifdef PNG_WRITE_FLUSH_SUPPORTED
-/* Set the automatic flush interval or 0 to turn flushing off */
-void PNGAPI
-png_set_flush(png_structrp png_ptr, int nrows)
-{
-   png_debug(1, "in png_set_flush");
-
-   if (png_ptr == NULL)
-      return;
-
-   png_ptr->flush_dist = (nrows < 0 ? 0 : nrows);
-}
-
-/* Flush the current output buffers now */
-void PNGAPI
-png_write_flush(png_structrp png_ptr)
-{
-   png_debug(1, "in png_write_flush");
-
-   if (png_ptr == NULL)
-      return;
-
-   /* We have already written out all of the data */
-   if (png_ptr->row_number >= png_ptr->num_rows)
-      return;
-
-   png_compress_IDAT(png_ptr, NULL, 0, Z_SYNC_FLUSH);
-   png_ptr->flush_rows = 0;
-   png_flush(png_ptr);
-}
-#endif /* PNG_WRITE_FLUSH_SUPPORTED */
-
-#ifdef PNG_WRITE_WEIGHTED_FILTER_SUPPORTED
-static void png_reset_filter_heuristics(png_structrp png_ptr);/* forward decl */
-#endif
-
-/* Free any memory used in png_ptr struct without freeing the struct itself. */
-static void
-png_write_destroy(png_structrp png_ptr)
-{
-   png_debug(1, "in png_write_destroy");
-
-   /* Free any memory zlib uses */
-   if (png_ptr->flags & PNG_FLAG_ZSTREAM_INITIALIZED)
-      deflateEnd(&png_ptr->zstream);
-
-   /* Free our memory.  png_free checks NULL for us. */
-   png_free_buffer_list(png_ptr, &png_ptr->zbuffer_list);
-   png_free(png_ptr, png_ptr->row_buf);
-#ifdef PNG_WRITE_FILTER_SUPPORTED
-   png_free(png_ptr, png_ptr->prev_row);
-   png_free(png_ptr, png_ptr->sub_row);
-   png_free(png_ptr, png_ptr->up_row);
-   png_free(png_ptr, png_ptr->avg_row);
-   png_free(png_ptr, png_ptr->paeth_row);
-#endif
-
-#ifdef PNG_WRITE_WEIGHTED_FILTER_SUPPORTED
-   /* Use this to save a little code space, it doesn't free the filter_costs */
-   png_reset_filter_heuristics(png_ptr);
-   png_free(png_ptr, png_ptr->filter_costs);
-   png_free(png_ptr, png_ptr->inv_filter_costs);
-#endif
-
-#ifdef PNG_SET_UNKNOWN_CHUNKS_SUPPORTED
-   png_free(png_ptr, png_ptr->chunk_list);
-#endif
-
-   /* The error handling and memory handling information is left intact at this
-    * point: the jmp_buf may still have to be freed.  See png_destroy_png_struct
-    * for how this happens.
-    */
-}
-
-/* Free all memory used by the write.
- * In libpng 1.6.0 this API changed quietly to no longer accept a NULL value for
- * *png_ptr_ptr.  Prior to 1.6.0 it would accept such a value and it would free
- * the passed in info_structs but it would quietly fail to free any of the data
- * inside them.  In 1.6.0 it quietly does nothing (it has to be quiet because it
- * has no png_ptr.)
- */
-void PNGAPI
-png_destroy_write_struct(png_structpp png_ptr_ptr, png_infopp info_ptr_ptr)
-{
-   png_debug(1, "in png_destroy_write_struct");
-
-   if (png_ptr_ptr != NULL)
-   {
-      png_structrp png_ptr = *png_ptr_ptr;
-
-      if (png_ptr != NULL) /* added in libpng 1.6.0 */
-      {
-         png_destroy_info_struct(png_ptr, info_ptr_ptr);
-
-         *png_ptr_ptr = NULL;
-         png_write_destroy(png_ptr);
-         png_destroy_png_struct(png_ptr);
-      }
-   }
-}
-
-/* Allow the application to select one or more row filters to use. */
-void PNGAPI
-png_set_filter(png_structrp png_ptr, int method, int filters)
-{
-   png_debug(1, "in png_set_filter");
-
-   if (png_ptr == NULL)
-      return;
-
-#ifdef PNG_MNG_FEATURES_SUPPORTED
-   if ((png_ptr->mng_features_permitted & PNG_FLAG_MNG_FILTER_64) &&
-       (method == PNG_INTRAPIXEL_DIFFERENCING))
-      method = PNG_FILTER_TYPE_BASE;
-
-#endif
-   if (method == PNG_FILTER_TYPE_BASE)
-   {
-      switch (filters & (PNG_ALL_FILTERS | 0x07))
-      {
-#ifdef PNG_WRITE_FILTER_SUPPORTED
-         case 5:
-         case 6:
-         case 7: png_app_error(png_ptr, "Unknown row filter for method 0");
-            /* FALL THROUGH */
-#endif /* PNG_WRITE_FILTER_SUPPORTED */
-         case PNG_FILTER_VALUE_NONE:
-            png_ptr->do_filter = PNG_FILTER_NONE; break;
-
-#ifdef PNG_WRITE_FILTER_SUPPORTED
-         case PNG_FILTER_VALUE_SUB:
-            png_ptr->do_filter = PNG_FILTER_SUB; break;
-
-         case PNG_FILTER_VALUE_UP:
-            png_ptr->do_filter = PNG_FILTER_UP; break;
-
-         case PNG_FILTER_VALUE_AVG:
-            png_ptr->do_filter = PNG_FILTER_AVG; break;
-
-         case PNG_FILTER_VALUE_PAETH:
-            png_ptr->do_filter = PNG_FILTER_PAETH; break;
-
-         default:
-            png_ptr->do_filter = (png_byte)filters; break;
-#else
-         default:
-            png_app_error(png_ptr, "Unknown row filter for method 0");
-#endif /* PNG_WRITE_FILTER_SUPPORTED */
-      }
-
-      /* If we have allocated the row_buf, this means we have already started
-       * with the image and we should have allocated all of the filter buffers
-       * that have been selected.  If prev_row isn't already allocated, then
-       * it is too late to start using the filters that need it, since we
-       * will be missing the data in the previous row.  If an application
-       * wants to start and stop using particular filters during compression,
-       * it should start out with all of the filters, and then add and
-       * remove them after the start of compression.
-       */
-      if (png_ptr->row_buf != NULL)
-      {
-#ifdef PNG_WRITE_FILTER_SUPPORTED
-         if ((png_ptr->do_filter & PNG_FILTER_SUB) && png_ptr->sub_row == NULL)
-         {
-            png_ptr->sub_row = (png_bytep)png_malloc(png_ptr,
-                (png_ptr->rowbytes + 1));
-            png_ptr->sub_row[0] = PNG_FILTER_VALUE_SUB;
-         }
-
-         if ((png_ptr->do_filter & PNG_FILTER_UP) && png_ptr->up_row == NULL)
-         {
-            if (png_ptr->prev_row == NULL)
-            {
-               png_warning(png_ptr, "Can't add Up filter after starting");
-               png_ptr->do_filter = (png_byte)(png_ptr->do_filter &
-                   ~PNG_FILTER_UP);
-            }
-
-            else
-            {
-               png_ptr->up_row = (png_bytep)png_malloc(png_ptr,
-                   (png_ptr->rowbytes + 1));
-               png_ptr->up_row[0] = PNG_FILTER_VALUE_UP;
-            }
-         }
-
-         if ((png_ptr->do_filter & PNG_FILTER_AVG) && png_ptr->avg_row == NULL)
-         {
-            if (png_ptr->prev_row == NULL)
-            {
-               png_warning(png_ptr, "Can't add Average filter after starting");
-               png_ptr->do_filter = (png_byte)(png_ptr->do_filter &
-                   ~PNG_FILTER_AVG);
-            }
-
-            else
-            {
-               png_ptr->avg_row = (png_bytep)png_malloc(png_ptr,
-                   (png_ptr->rowbytes + 1));
-               png_ptr->avg_row[0] = PNG_FILTER_VALUE_AVG;
-            }
-         }
-
-         if ((png_ptr->do_filter & PNG_FILTER_PAETH) &&
-             png_ptr->paeth_row == NULL)
-         {
-            if (png_ptr->prev_row == NULL)
-            {
-               png_warning(png_ptr, "Can't add Paeth filter after starting");
-               png_ptr->do_filter &= (png_byte)(~PNG_FILTER_PAETH);
-            }
-
-            else
-            {
-               png_ptr->paeth_row = (png_bytep)png_malloc(png_ptr,
-                   (png_ptr->rowbytes + 1));
-               png_ptr->paeth_row[0] = PNG_FILTER_VALUE_PAETH;
-            }
-         }
-
-         if (png_ptr->do_filter == PNG_NO_FILTERS)
-#endif /* PNG_WRITE_FILTER_SUPPORTED */
-            png_ptr->do_filter = PNG_FILTER_NONE;
-      }
-   }
-   else
-      png_error(png_ptr, "Unknown custom filter method");
-}
-
-/* This allows us to influence the way in which libpng chooses the "best"
- * filter for the current scanline.  While the "minimum-sum-of-absolute-
- * differences metric is relatively fast and effective, there is some
- * question as to whether it can be improved upon by trying to keep the
- * filtered data going to zlib more consistent, hopefully resulting in
- * better compression.
- */
-#ifdef PNG_WRITE_WEIGHTED_FILTER_SUPPORTED      /* GRR 970116 */
-/* Convenience reset API. */
-static void
-png_reset_filter_heuristics(png_structrp png_ptr)
-{
-   /* Clear out any old values in the 'weights' - this must be done because if
-    * the app calls set_filter_heuristics multiple times with different
-    * 'num_weights' values we would otherwise potentially have wrong sized
-    * arrays.
-    */
-   png_ptr->num_prev_filters = 0;
-   png_ptr->heuristic_method = PNG_FILTER_HEURISTIC_UNWEIGHTED;
-   if (png_ptr->prev_filters != NULL)
-   {
-      png_bytep old = png_ptr->prev_filters;
-      png_ptr->prev_filters = NULL;
-      png_free(png_ptr, old);
-   }
-   if (png_ptr->filter_weights != NULL)
-   {
-      png_uint_16p old = png_ptr->filter_weights;
-      png_ptr->filter_weights = NULL;
-      png_free(png_ptr, old);
-   }
-
-   if (png_ptr->inv_filter_weights != NULL)
-   {
-      png_uint_16p old = png_ptr->inv_filter_weights;
-      png_ptr->inv_filter_weights = NULL;
-      png_free(png_ptr, old);
-   }
-
-   /* Leave the filter_costs - this array is fixed size. */
-}
-
-static int
-png_init_filter_heuristics(png_structrp png_ptr, int heuristic_method,
-   int num_weights)
-{
-   if (png_ptr == NULL)
-      return 0;
-
-   /* Clear out the arrays */
-   png_reset_filter_heuristics(png_ptr);
-
-   /* Check arguments; the 'reset' function makes the correct settings for the
-    * unweighted case, but we must handle the weight case by initializing the
-    * arrays for the caller.
-    */
-   if (heuristic_method == PNG_FILTER_HEURISTIC_WEIGHTED)
-   {
-      int i;
-
-      if (num_weights > 0)
-      {
-         png_ptr->prev_filters = (png_bytep)png_malloc(png_ptr,
-             (png_uint_32)((sizeof (png_byte)) * num_weights));
-
-         /* To make sure that the weighting starts out fairly */
-         for (i = 0; i < num_weights; i++)
-         {
-            png_ptr->prev_filters[i] = 255;
-         }
-
-         png_ptr->filter_weights = (png_uint_16p)png_malloc(png_ptr,
-             (png_uint_32)((sizeof (png_uint_16)) * num_weights));
-
-         png_ptr->inv_filter_weights = (png_uint_16p)png_malloc(png_ptr,
-             (png_uint_32)((sizeof (png_uint_16)) * num_weights));
-
-         for (i = 0; i < num_weights; i++)
-         {
-            png_ptr->inv_filter_weights[i] =
-            png_ptr->filter_weights[i] = PNG_WEIGHT_FACTOR;
-         }
-
-         /* Safe to set this now */
-         png_ptr->num_prev_filters = (png_byte)num_weights;
-      }
-
-      /* If, in the future, there are other filter methods, this would
-       * need to be based on png_ptr->filter.
-       */
-      if (png_ptr->filter_costs == NULL)
-      {
-         png_ptr->filter_costs = (png_uint_16p)png_malloc(png_ptr,
-             (png_uint_32)((sizeof (png_uint_16)) * PNG_FILTER_VALUE_LAST));
-
-         png_ptr->inv_filter_costs = (png_uint_16p)png_malloc(png_ptr,
-             (png_uint_32)((sizeof (png_uint_16)) * PNG_FILTER_VALUE_LAST));
-      }
-
-      for (i = 0; i < PNG_FILTER_VALUE_LAST; i++)
-      {
-         png_ptr->inv_filter_costs[i] =
-         png_ptr->filter_costs[i] = PNG_COST_FACTOR;
-      }
-
-      /* All the arrays are inited, safe to set this: */
-      png_ptr->heuristic_method = PNG_FILTER_HEURISTIC_WEIGHTED;
-
-      /* Return the 'ok' code. */
-      return 1;
-   }
-   else if (heuristic_method == PNG_FILTER_HEURISTIC_DEFAULT ||
-      heuristic_method == PNG_FILTER_HEURISTIC_UNWEIGHTED)
-   {
-      return 1;
-   }
-   else
-   {
-      png_warning(png_ptr, "Unknown filter heuristic method");
-      return 0;
-   }
-}
-
-/* Provide floating and fixed point APIs */
-#ifdef PNG_FLOATING_POINT_SUPPORTED
-void PNGAPI
-png_set_filter_heuristics(png_structrp png_ptr, int heuristic_method,
-    int num_weights, png_const_doublep filter_weights,
-    png_const_doublep filter_costs)
-{
-   png_debug(1, "in png_set_filter_heuristics");
-
-   /* The internal API allocates all the arrays and ensures that the elements of
-    * those arrays are set to the default value.
-    */
-   if (!png_init_filter_heuristics(png_ptr, heuristic_method, num_weights))
-      return;
-
-   /* If using the weighted method copy in the weights. */
-   if (heuristic_method == PNG_FILTER_HEURISTIC_WEIGHTED)
-   {
-      int i;
-      for (i = 0; i < num_weights; i++)
-      {
-         if (filter_weights[i] <= 0.0)
-         {
-            png_ptr->inv_filter_weights[i] =
-            png_ptr->filter_weights[i] = PNG_WEIGHT_FACTOR;
-         }
-
-         else
-         {
-            png_ptr->inv_filter_weights[i] =
-                (png_uint_16)(PNG_WEIGHT_FACTOR*filter_weights[i]+.5);
-
-            png_ptr->filter_weights[i] =
-                (png_uint_16)(PNG_WEIGHT_FACTOR/filter_weights[i]+.5);
-         }
-      }
-
-      /* Here is where we set the relative costs of the different filters.  We
-       * should take the desired compression level into account when setting
-       * the costs, so that Paeth, for instance, has a high relative cost at low
-       * compression levels, while it has a lower relative cost at higher
-       * compression settings.  The filter types are in order of increasing
-       * relative cost, so it would be possible to do this with an algorithm.
-       */
-      for (i = 0; i < PNG_FILTER_VALUE_LAST; i++) if (filter_costs[i] >= 1.0)
-      {
-         png_ptr->inv_filter_costs[i] =
-             (png_uint_16)(PNG_COST_FACTOR / filter_costs[i] + .5);
-
-         png_ptr->filter_costs[i] =
-             (png_uint_16)(PNG_COST_FACTOR * filter_costs[i] + .5);
-      }
-   }
-}
-#endif /* FLOATING_POINT */
-
-#ifdef PNG_FIXED_POINT_SUPPORTED
-void PNGAPI
-png_set_filter_heuristics_fixed(png_structrp png_ptr, int heuristic_method,
-    int num_weights, png_const_fixed_point_p filter_weights,
-    png_const_fixed_point_p filter_costs)
-{
-   png_debug(1, "in png_set_filter_heuristics_fixed");
-
-   /* The internal API allocates all the arrays and ensures that the elements of
-    * those arrays are set to the default value.
-    */
-   if (!png_init_filter_heuristics(png_ptr, heuristic_method, num_weights))
-      return;
-
-   /* If using the weighted method copy in the weights. */
-   if (heuristic_method == PNG_FILTER_HEURISTIC_WEIGHTED)
-   {
-      int i;
-      for (i = 0; i < num_weights; i++)
-      {
-         if (filter_weights[i] <= 0)
-         {
-            png_ptr->inv_filter_weights[i] =
-            png_ptr->filter_weights[i] = PNG_WEIGHT_FACTOR;
-         }
-
-         else
-         {
-            png_ptr->inv_filter_weights[i] = (png_uint_16)
-               ((PNG_WEIGHT_FACTOR*filter_weights[i]+PNG_FP_HALF)/PNG_FP_1);
-
-            png_ptr->filter_weights[i] = (png_uint_16)((PNG_WEIGHT_FACTOR*
-               PNG_FP_1+(filter_weights[i]/2))/filter_weights[i]);
-         }
-      }
-
-      /* Here is where we set the relative costs of the different filters.  We
-       * should take the desired compression level into account when setting
-       * the costs, so that Paeth, for instance, has a high relative cost at low
-       * compression levels, while it has a lower relative cost at higher
-       * compression settings.  The filter types are in order of increasing
-       * relative cost, so it would be possible to do this with an algorithm.
-       */
-      for (i = 0; i < PNG_FILTER_VALUE_LAST; i++)
-         if (filter_costs[i] >= PNG_FP_1)
-      {
-         png_uint_32 tmp;
-
-         /* Use a 32 bit unsigned temporary here because otherwise the
-          * intermediate value will be a 32 bit *signed* integer (ANSI rules)
-          * and this will get the wrong answer on division.
-          */
-         tmp = PNG_COST_FACTOR*PNG_FP_1 + (filter_costs[i]/2);
-         tmp /= filter_costs[i];
-
-         png_ptr->inv_filter_costs[i] = (png_uint_16)tmp;
-
-         tmp = PNG_COST_FACTOR * filter_costs[i] + PNG_FP_HALF;
-         tmp /= PNG_FP_1;
-
-         png_ptr->filter_costs[i] = (png_uint_16)tmp;
-      }
-   }
-}
-#endif /* FIXED_POINT */
-#endif /* PNG_WRITE_WEIGHTED_FILTER_SUPPORTED */
-
-void PNGAPI
-png_set_compression_level(png_structrp png_ptr, int level)
-{
-   png_debug(1, "in png_set_compression_level");
-
-   if (png_ptr == NULL)
-      return;
-
-   png_ptr->zlib_level = level;
-}
-
-void PNGAPI
-png_set_compression_mem_level(png_structrp png_ptr, int mem_level)
-{
-   png_debug(1, "in png_set_compression_mem_level");
-
-   if (png_ptr == NULL)
-      return;
-
-   png_ptr->zlib_mem_level = mem_level;
-}
-
-void PNGAPI
-png_set_compression_strategy(png_structrp png_ptr, int strategy)
-{
-   png_debug(1, "in png_set_compression_strategy");
-
-   if (png_ptr == NULL)
-      return;
-
-   /* The flag setting here prevents the libpng dynamic selection of strategy.
-    */
-   png_ptr->flags |= PNG_FLAG_ZLIB_CUSTOM_STRATEGY;
-   png_ptr->zlib_strategy = strategy;
-}
-
-/* If PNG_WRITE_OPTIMIZE_CMF_SUPPORTED is defined, libpng will use a
- * smaller value of window_bits if it can do so safely.
- */
-void PNGAPI
-png_set_compression_window_bits(png_structrp png_ptr, int window_bits)
-{
-   if (png_ptr == NULL)
-      return;
-
-   /* Prior to 1.6.0 this would warn but then set the window_bits value, this
-    * meant that negative window bits values could be selected which would cause
-    * libpng to write a non-standard PNG file with raw deflate or gzip
-    * compressed IDAT or ancillary chunks.  Such files can be read and there is
-    * no warning on read, so this seems like a very bad idea.
-    */
-   if (window_bits > 15)
-   {
-      png_warning(png_ptr, "Only compression windows <= 32k supported by PNG");
-      window_bits = 15;
-   }
-
-   else if (window_bits < 8)
-   {
-      png_warning(png_ptr, "Only compression windows >= 256 supported by PNG");
-      window_bits = 8;
-   }
-
-   png_ptr->zlib_window_bits = window_bits;
-}
-
-void PNGAPI
-png_set_compression_method(png_structrp png_ptr, int method)
-{
-   png_debug(1, "in png_set_compression_method");
-
-   if (png_ptr == NULL)
-      return;
-
-   /* This would produce an invalid PNG file if it worked, but it doesn't and
-    * deflate will fault it, so it is harmless to just warn here.
-    */
-   if (method != 8)
-      png_warning(png_ptr, "Only compression method 8 is supported by PNG");
-
-   png_ptr->zlib_method = method;
-}
-
-/* The following were added to libpng-1.5.4 */
-#ifdef PNG_WRITE_CUSTOMIZE_ZTXT_COMPRESSION_SUPPORTED
-void PNGAPI
-png_set_text_compression_level(png_structrp png_ptr, int level)
-{
-   png_debug(1, "in png_set_text_compression_level");
-
-   if (png_ptr == NULL)
-      return;
-
-   png_ptr->zlib_text_level = level;
-}
-
-void PNGAPI
-png_set_text_compression_mem_level(png_structrp png_ptr, int mem_level)
-{
-   png_debug(1, "in png_set_text_compression_mem_level");
-
-   if (png_ptr == NULL)
-      return;
-
-   png_ptr->zlib_text_mem_level = mem_level;
-}
-
-void PNGAPI
-png_set_text_compression_strategy(png_structrp png_ptr, int strategy)
-{
-   png_debug(1, "in png_set_text_compression_strategy");
-
-   if (png_ptr == NULL)
-      return;
-
-   png_ptr->zlib_text_strategy = strategy;
-}
-
-/* If PNG_WRITE_OPTIMIZE_CMF_SUPPORTED is defined, libpng will use a
- * smaller value of window_bits if it can do so safely.
- */
-void PNGAPI
-png_set_text_compression_window_bits(png_structrp png_ptr, int window_bits)
-{
-   if (png_ptr == NULL)
-      return;
-
-   if (window_bits > 15)
-   {
-      png_warning(png_ptr, "Only compression windows <= 32k supported by PNG");
-      window_bits = 15;
-   }
-
-   else if (window_bits < 8)
-   {
-      png_warning(png_ptr, "Only compression windows >= 256 supported by PNG");
-      window_bits = 8;
-   }
-
-   png_ptr->zlib_text_window_bits = window_bits;
-}
-
-void PNGAPI
-png_set_text_compression_method(png_structrp png_ptr, int method)
-{
-   png_debug(1, "in png_set_text_compression_method");
-
-   if (png_ptr == NULL)
-      return;
-
-   if (method != 8)
-      png_warning(png_ptr, "Only compression method 8 is supported by PNG");
-
-   png_ptr->zlib_text_method = method;
-}
-#endif /* PNG_WRITE_CUSTOMIZE_ZTXT_COMPRESSION_SUPPORTED */
-/* end of API added to libpng-1.5.4 */
-
-void PNGAPI
-png_set_write_status_fn(png_structrp png_ptr, png_write_status_ptr write_row_fn)
-{
-   if (png_ptr == NULL)
-      return;
-
-   png_ptr->write_row_fn = write_row_fn;
-}
-
-#ifdef PNG_WRITE_USER_TRANSFORM_SUPPORTED
-void PNGAPI
-png_set_write_user_transform_fn(png_structrp png_ptr, png_user_transform_ptr
-    write_user_transform_fn)
-{
-   png_debug(1, "in png_set_write_user_transform_fn");
-
-   if (png_ptr == NULL)
-      return;
-
-   png_ptr->transformations |= PNG_USER_TRANSFORM;
-   png_ptr->write_user_transform_fn = write_user_transform_fn;
-}
-#endif
-
-
-#ifdef PNG_INFO_IMAGE_SUPPORTED
-void PNGAPI
-png_write_png(png_structrp png_ptr, png_inforp info_ptr,
-    int transforms, voidp params)
-{
-   if (png_ptr == NULL || info_ptr == NULL)
-      return;
-
-   /* Write the file header information. */
-   png_write_info(png_ptr, info_ptr);
-
-   /* ------ these transformations don't touch the info structure ------- */
-
-#ifdef PNG_WRITE_INVERT_SUPPORTED
-   /* Invert monochrome pixels */
-   if (transforms & PNG_TRANSFORM_INVERT_MONO)
-      png_set_invert_mono(png_ptr);
-#endif
-
-#ifdef PNG_WRITE_SHIFT_SUPPORTED
-   /* Shift the pixels up to a legal bit depth and fill in
-    * as appropriate to correctly scale the image.
-    */
-   if ((transforms & PNG_TRANSFORM_SHIFT)
-       && (info_ptr->valid & PNG_INFO_sBIT))
-      png_set_shift(png_ptr, &info_ptr->sig_bit);
-#endif
-
-#ifdef PNG_WRITE_PACK_SUPPORTED
-   /* Pack pixels into bytes */
-   if (transforms & PNG_TRANSFORM_PACKING)
-       png_set_packing(png_ptr);
-#endif
-
-#ifdef PNG_WRITE_SWAP_ALPHA_SUPPORTED
-   /* Swap location of alpha bytes from ARGB to RGBA */
-   if (transforms & PNG_TRANSFORM_SWAP_ALPHA)
-      png_set_swap_alpha(png_ptr);
-#endif
-
-#ifdef PNG_WRITE_FILLER_SUPPORTED
-   /* Pack XRGB/RGBX/ARGB/RGBA into RGB (4 channels -> 3 channels) */
-   if (transforms & PNG_TRANSFORM_STRIP_FILLER_AFTER)
-      png_set_filler(png_ptr, 0, PNG_FILLER_AFTER);
-
-   else if (transforms & PNG_TRANSFORM_STRIP_FILLER_BEFORE)
-      png_set_filler(png_ptr, 0, PNG_FILLER_BEFORE);
-#endif
-
-#ifdef PNG_WRITE_BGR_SUPPORTED
-   /* Flip BGR pixels to RGB */
-   if (transforms & PNG_TRANSFORM_BGR)
-      png_set_bgr(png_ptr);
-#endif
-
-#ifdef PNG_WRITE_SWAP_SUPPORTED
-   /* Swap bytes of 16-bit files to most significant byte first */
-   if (transforms & PNG_TRANSFORM_SWAP_ENDIAN)
-      png_set_swap(png_ptr);
-#endif
-
-#ifdef PNG_WRITE_PACKSWAP_SUPPORTED
-   /* Swap bits of 1, 2, 4 bit packed pixel formats */
-   if (transforms & PNG_TRANSFORM_PACKSWAP)
-      png_set_packswap(png_ptr);
-#endif
-
-#ifdef PNG_WRITE_INVERT_ALPHA_SUPPORTED
-   /* Invert the alpha channel from opacity to transparency */
-   if (transforms & PNG_TRANSFORM_INVERT_ALPHA)
-      png_set_invert_alpha(png_ptr);
-#endif
-
-   /* ----------------------- end of transformations ------------------- */
-
-   /* Write the bits */
-   if (info_ptr->valid & PNG_INFO_IDAT)
-       png_write_image(png_ptr, info_ptr->row_pointers);
-
-   /* It is REQUIRED to call this to finish writing the rest of the file */
-   png_write_end(png_ptr, info_ptr);
-
-   PNG_UNUSED(transforms)   /* Quiet compiler warnings */
-   PNG_UNUSED(params)
-}
-#endif
-
-
-#ifdef PNG_SIMPLIFIED_WRITE_SUPPORTED
-#ifdef PNG_STDIO_SUPPORTED /* currently required for png_image_write_* */
-/* Initialize the write structure - general purpose utility. */
-static int
-png_image_write_init(png_imagep image)
-{
-   png_structp png_ptr = png_create_write_struct(PNG_LIBPNG_VER_STRING, image,
-          png_safe_error, png_safe_warning);
-
-   if (png_ptr != NULL)
-   {
-      png_infop info_ptr = png_create_info_struct(png_ptr);
-
-      if (info_ptr != NULL)
-      {
-         png_controlp control = png_voidcast(png_controlp,
-            png_malloc_warn(png_ptr, (sizeof *control)));
-
-         if (control != NULL)
-         {
-            memset(control, 0, (sizeof *control));
-
-            control->png_ptr = png_ptr;
-            control->info_ptr = info_ptr;
-            control->for_write = 1;
-
-            image->opaque = control;
-            return 1;
-         }
-
-         /* Error clean up */
-         png_destroy_info_struct(png_ptr, &info_ptr);
-      }
-
-      png_destroy_write_struct(&png_ptr, NULL);
-   }
-
-   return png_image_error(image, "png_image_write_: out of memory");
-}
-
-/* Arguments to png_image_write_main: */
-typedef struct
-{
-   /* Arguments: */
-   png_imagep      image;
-   png_const_voidp buffer;
-   png_int_32      row_stride;
-   png_const_voidp colormap;
-   int             convert_to_8bit;
-   /* Local variables: */
-   png_const_voidp first_row;
-   ptrdiff_t       row_bytes;
-   png_voidp       local_row;
-} png_image_write_control;
-
-/* Write png_uint_16 input to a 16-bit PNG; the png_ptr has already been set to
- * do any necessary byte swapping.  The component order is defined by the
- * png_image format value.
- */
-static int
-png_write_image_16bit(png_voidp argument)
-{
-   png_image_write_control *display = png_voidcast(png_image_write_control*,
-      argument);
-   png_imagep image = display->image;
-   png_structrp png_ptr = image->opaque->png_ptr;
-
-   png_const_uint_16p input_row = png_voidcast(png_const_uint_16p,
-      display->first_row);
-   png_uint_16p output_row = png_voidcast(png_uint_16p, display->local_row);
-   png_uint_16p row_end;
-   const int channels = (image->format & PNG_FORMAT_FLAG_COLOR) ? 3 : 1;
-   int aindex = 0;
-   png_uint_32 y = image->height;
-
-   if (image->format & PNG_FORMAT_FLAG_ALPHA)
-   {
-      if (image->format & PNG_FORMAT_FLAG_AFIRST)
-      {
-         aindex = -1;
-         ++input_row; /* To point to the first component */
-         ++output_row;
-      }
-
-      else
-         aindex = channels;
-   }
-
-   else
-      png_error(png_ptr, "png_write_image: internal call error");
-
-   /* Work out the output row end and count over this, note that the increment
-    * above to 'row' means that row_end can actually be beyond the end of the
-    * row; this is correct.
-    */
-   row_end = output_row + image->width * (channels+1);
-
-   while (y-- > 0)
-   {
-      png_const_uint_16p in_ptr = input_row;
-      png_uint_16p out_ptr = output_row;
-
-      while (out_ptr < row_end)
-      {
-         const png_uint_16 alpha = in_ptr[aindex];
-         png_uint_32 reciprocal = 0;
-         int c;
-
-         out_ptr[aindex] = alpha;
-
-         /* Calculate a reciprocal.  The correct calculation is simply
-          * component/alpha*65535 << 15. (I.e. 15 bits of precision); this
-          * allows correct rounding by adding .5 before the shift.  'reciprocal'
-          * is only initialized when required.
-          */
-         if (alpha > 0 && alpha < 65535)
-            reciprocal = ((0xffff<<15)+(alpha>>1))/alpha;
-
-         c = channels;
-         do /* always at least one channel */
-         {
-            png_uint_16 component = *in_ptr++;
-
-            /* The following gives 65535 for an alpha of 0, which is fine,
-             * otherwise if 0/0 is represented as some other value there is more
-             * likely to be a discontinuity which will probably damage
-             * compression when moving from a fully transparent area to a
-             * nearly transparent one.  (The assumption here is that opaque
-             * areas tend not to be 0 intensity.)
-             */
-            if (component >= alpha)
-               component = 65535;
-
-            /* component<alpha, so component/alpha is less than one and
-             * component*reciprocal is less than 2^31.
-             */
-            else if (component > 0 && alpha < 65535)
-            {
-               png_uint_32 calc = component * reciprocal;
-               calc += 16384; /* round to nearest */
-               component = (png_uint_16)(calc >> 15);
-            }
-
-            *out_ptr++ = component;
-         }
-         while (--c > 0);
-
-         /* Skip to next component (skip the intervening alpha channel) */
-         ++in_ptr;
-         ++out_ptr;
-      }
-
-      png_write_row(png_ptr, png_voidcast(png_const_bytep, display->local_row));
-      input_row += display->row_bytes/(sizeof (png_uint_16));
-   }
-
-   return 1;
-}
-
-/* Given 16-bit input (1 to 4 channels) write 8-bit output.  If an alpha channel
- * is present it must be removed from the components, the components are then
- * written in sRGB encoding.  No components are added or removed.
- *
- * Calculate an alpha reciprocal to reverse pre-multiplication.  As above the
- * calculation can be done to 15 bits of accuracy; however, the output needs to
- * be scaled in the range 0..255*65535, so include that scaling here.
- */
-#define UNP_RECIPROCAL(alpha) ((((0xffff*0xff)<<7)+(alpha>>1))/alpha)
-
-static png_byte
-png_unpremultiply(png_uint_32 component, png_uint_32 alpha,
-   png_uint_32 reciprocal/*from the above macro*/)
-{
-   /* The following gives 1.0 for an alpha of 0, which is fine, otherwise if 0/0
-    * is represented as some other value there is more likely to be a
-    * discontinuity which will probably damage compression when moving from a
-    * fully transparent area to a nearly transparent one.  (The assumption here
-    * is that opaque areas tend not to be 0 intensity.)
-    *
-    * There is a rounding problem here; if alpha is less than 128 it will end up
-    * as 0 when scaled to 8 bits.  To avoid introducing spurious colors into the
-    * output change for this too.
-    */
-   if (component >= alpha || alpha < 128)
-      return 255;
-
-   /* component<alpha, so component/alpha is less than one and
-    * component*reciprocal is less than 2^31.
-    */
-   else if (component > 0)
-   {
-      /* The test is that alpha/257 (rounded) is less than 255, the first value
-       * that becomes 255 is 65407.
-       * NOTE: this must agree with the PNG_DIV257 macro (which must, therefore,
-       * be exact!)  [Could also test reciprocal != 0]
-       */
-      if (alpha < 65407)
-      {
-         component *= reciprocal;
-         component += 64; /* round to nearest */
-         component >>= 7;
-      }
-
-      else
-         component *= 255;
-
-      /* Convert the component to sRGB. */
-      return (png_byte)PNG_sRGB_FROM_LINEAR(component);
-   }
-
-   else
-      return 0;
-}
-
-static int
-png_write_image_8bit(png_voidp argument)
-{
-   png_image_write_control *display = png_voidcast(png_image_write_control*,
-      argument);
-   png_imagep image = display->image;
-   png_structrp png_ptr = image->opaque->png_ptr;
-
-   png_const_uint_16p input_row = png_voidcast(png_const_uint_16p,
-      display->first_row);
-   png_bytep output_row = png_voidcast(png_bytep, display->local_row);
-   png_uint_32 y = image->height;
-   const int channels = (image->format & PNG_FORMAT_FLAG_COLOR) ? 3 : 1;
-
-   if (image->format & PNG_FORMAT_FLAG_ALPHA)
-   {
-      png_bytep row_end;
-      int aindex;
-
-      if (image->format & PNG_FORMAT_FLAG_AFIRST)
-      {
-         aindex = -1;
-         ++input_row; /* To point to the first component */
-         ++output_row;
-      }
-
-      else
-         aindex = channels;
-
-      /* Use row_end in place of a loop counter: */
-      row_end = output_row + image->width * (channels+1);
-
-      while (y-- > 0)
-      {
-         png_const_uint_16p in_ptr = input_row;
-         png_bytep out_ptr = output_row;
-
-         while (out_ptr < row_end)
-         {
-            png_uint_16 alpha = in_ptr[aindex];
-            png_byte alphabyte = (png_byte)PNG_DIV257(alpha);
-            png_uint_32 reciprocal = 0;
-            int c;
-
-            /* Scale and write the alpha channel. */
-            out_ptr[aindex] = alphabyte;
-
-            if (alphabyte > 0 && alphabyte < 255)
-               reciprocal = UNP_RECIPROCAL(alpha);
-
-            c = channels;
-            do /* always at least one channel */
-               *out_ptr++ = png_unpremultiply(*in_ptr++, alpha, reciprocal);
-            while (--c > 0);
-
-            /* Skip to next component (skip the intervening alpha channel) */
-            ++in_ptr;
-            ++out_ptr;
-         } /* while out_ptr < row_end */
-
-         png_write_row(png_ptr, png_voidcast(png_const_bytep,
-            display->local_row));
-         input_row += display->row_bytes/(sizeof (png_uint_16));
-      } /* while y */
-   }
-
-   else
-   {
-      /* No alpha channel, so the row_end really is the end of the row and it
-       * is sufficient to loop over the components one by one.
-       */
-      png_bytep row_end = output_row + image->width * channels;
-
-      while (y-- > 0)
-      {
-         png_const_uint_16p in_ptr = input_row;
-         png_bytep out_ptr = output_row;
-
-         while (out_ptr < row_end)
-         {
-            png_uint_32 component = *in_ptr++;
-
-            component *= 255;
-            *out_ptr++ = (png_byte)PNG_sRGB_FROM_LINEAR(component);
-         }
-
-         png_write_row(png_ptr, output_row);
-         input_row += display->row_bytes/(sizeof (png_uint_16));
-      }
-   }
-
-   return 1;
-}
-
-static void
-png_image_set_PLTE(png_image_write_control *display)
-{
-   const png_imagep image = display->image;
-   const void *cmap = display->colormap;
-   const int entries = image->colormap_entries > 256 ? 256 :
-      (int)image->colormap_entries;
-
-   /* NOTE: the caller must check for cmap != NULL and entries != 0 */
-   const png_uint_32 format = image->format;
-   const int channels = PNG_IMAGE_SAMPLE_CHANNELS(format);
-
-#  ifdef PNG_FORMAT_BGR_SUPPORTED
-      const int afirst = (format & PNG_FORMAT_FLAG_AFIRST) != 0 &&
-         (format & PNG_FORMAT_FLAG_ALPHA) != 0;
-#  else
-#     define afirst 0
-#  endif
-
-#  ifdef PNG_FORMAT_BGR_SUPPORTED
-      const int bgr = (format & PNG_FORMAT_FLAG_BGR) ? 2 : 0;
-#  else
-#     define bgr 0
-#  endif
-
-   int i, num_trans;
-   png_color palette[256];
-   png_byte tRNS[256];
-
-   memset(tRNS, 255, (sizeof tRNS));
-   memset(palette, 0, (sizeof palette));
-
-   for (i=num_trans=0; i<entries; ++i)
-   {
-      /* This gets automatically converted to sRGB with reversal of the
-       * pre-multiplication if the color-map has an alpha channel.
-       */
-      if (format & PNG_FORMAT_FLAG_LINEAR)
-      {
-         png_const_uint_16p entry = png_voidcast(png_const_uint_16p, cmap);
-
-         entry += i * channels;
-
-         if (channels & 1) /* no alpha */
-         {
-            if (channels >= 3) /* RGB */
-            {
-               palette[i].blue = (png_byte)PNG_sRGB_FROM_LINEAR(255 *
-                  entry[(2 ^ bgr)]);
-               palette[i].green = (png_byte)PNG_sRGB_FROM_LINEAR(255 *
-                  entry[1]);
-               palette[i].red = (png_byte)PNG_sRGB_FROM_LINEAR(255 *
-                  entry[bgr]);
-            }
-
-            else /* Gray */
-               palette[i].blue = palette[i].red = palette[i].green =
-                  (png_byte)PNG_sRGB_FROM_LINEAR(255 * *entry);
-         }
-
-         else /* alpha */
-         {
-            png_uint_16 alpha = entry[afirst ? 0 : channels-1];
-            png_byte alphabyte = (png_byte)PNG_DIV257(alpha);
-            png_uint_32 reciprocal = 0;
-
-            /* Calculate a reciprocal, as in the png_write_image_8bit code above
-             * this is designed to produce a value scaled to 255*65535 when
-             * divided by 128 (i.e. asr 7).
-             */
-            if (alphabyte > 0 && alphabyte < 255)
-               reciprocal = (((0xffff*0xff)<<7)+(alpha>>1))/alpha;
-
-            tRNS[i] = alphabyte;
-            if (alphabyte < 255)
-               num_trans = i+1;
-
-            if (channels >= 3) /* RGB */
-            {
-               palette[i].blue = png_unpremultiply(entry[afirst + (2 ^ bgr)],
-                  alpha, reciprocal);
-               palette[i].green = png_unpremultiply(entry[afirst + 1], alpha,
-                  reciprocal);
-               palette[i].red = png_unpremultiply(entry[afirst + bgr], alpha,
-                  reciprocal);
-            }
-
-            else /* gray */
-               palette[i].blue = palette[i].red = palette[i].green =
-                  png_unpremultiply(entry[afirst], alpha, reciprocal);
-         }
-      }
-
-      else /* Color-map has sRGB values */
-      {
-         png_const_bytep entry = png_voidcast(png_const_bytep, cmap);
-
-         entry += i * channels;
-
-         switch (channels)
-         {
-            case 4:
-               tRNS[i] = entry[afirst ? 0 : 3];
-               if (tRNS[i] < 255)
-                  num_trans = i+1;
-               /* FALL THROUGH */
-            case 3:
-               palette[i].blue = entry[afirst + (2 ^ bgr)];
-               palette[i].green = entry[afirst + 1];
-               palette[i].red = entry[afirst + bgr];
-               break;
-
-            case 2:
-               tRNS[i] = entry[1 ^ afirst];
-               if (tRNS[i] < 255)
-                  num_trans = i+1;
-               /* FALL THROUGH */
-            case 1:
-               palette[i].blue = palette[i].red = palette[i].green =
-                  entry[afirst];
-               break;
-
-            default:
-               break;
-         }
-      }
-   }
-
-#  ifdef afirst
-#     undef afirst
-#  endif
-#  ifdef bgr
-#     undef bgr
-#  endif
-
-   png_set_PLTE(image->opaque->png_ptr, image->opaque->info_ptr, palette,
-      entries);
-
-   if (num_trans > 0)
-      png_set_tRNS(image->opaque->png_ptr, image->opaque->info_ptr, tRNS,
-         num_trans, NULL);
-
-   image->colormap_entries = entries;
-}
-
-static int
-png_image_write_main(png_voidp argument)
-{
-   png_image_write_control *display = png_voidcast(png_image_write_control*,
-      argument);
-   png_imagep image = display->image;
-   png_structrp png_ptr = image->opaque->png_ptr;
-   png_inforp info_ptr = image->opaque->info_ptr;
-   png_uint_32 format = image->format;
-
-   int colormap = (format & PNG_FORMAT_FLAG_COLORMAP) != 0;
-   int linear = !colormap && (format & PNG_FORMAT_FLAG_LINEAR) != 0; /* input */
-   int alpha = !colormap && (format & PNG_FORMAT_FLAG_ALPHA) != 0;
-   int write_16bit = linear && !colormap && !display->convert_to_8bit;
-
-#  ifdef PNG_BENIGN_ERRORS_SUPPORTED
-      /* Make sure we error out on any bad situation */
-      png_set_benign_errors(png_ptr, 0/*error*/);
-#  endif
-
-   /* Default the 'row_stride' parameter if required. */
-   if (display->row_stride == 0)
-      display->row_stride = PNG_IMAGE_ROW_STRIDE(*image);
-
-   /* Set the required transforms then write the rows in the correct order. */
-   if (format & PNG_FORMAT_FLAG_COLORMAP)
-   {
-      if (display->colormap != NULL && image->colormap_entries > 0)
-      {
-         png_uint_32 entries = image->colormap_entries;
-
-         png_set_IHDR(png_ptr, info_ptr, image->width, image->height,
-            entries > 16 ? 8 : (entries > 4 ? 4 : (entries > 2 ? 2 : 1)),
-            PNG_COLOR_TYPE_PALETTE, PNG_INTERLACE_NONE,
-            PNG_COMPRESSION_TYPE_BASE, PNG_FILTER_TYPE_BASE);
-
-         png_image_set_PLTE(display);
-      }
-
-      else
-         png_error(image->opaque->png_ptr,
-            "no color-map for color-mapped image");
-   }
-
-   else
-      png_set_IHDR(png_ptr, info_ptr, image->width, image->height,
-         write_16bit ? 16 : 8,
-         ((format & PNG_FORMAT_FLAG_COLOR) ? PNG_COLOR_MASK_COLOR : 0) +
-         ((format & PNG_FORMAT_FLAG_ALPHA) ? PNG_COLOR_MASK_ALPHA : 0),
-         PNG_INTERLACE_NONE, PNG_COMPRESSION_TYPE_BASE, PNG_FILTER_TYPE_BASE);
-
-   /* Counter-intuitively the data transformations must be called *after*
-    * png_write_info, not before as in the read code, but the 'set' functions
-    * must still be called before.  Just set the color space information, never
-    * write an interlaced image.
-    */
-
-   if (write_16bit)
-   {
-      /* The gamma here is 1.0 (linear) and the cHRM chunk matches sRGB. */
-      png_set_gAMA_fixed(png_ptr, info_ptr, PNG_GAMMA_LINEAR);
-
-      if (!(image->flags & PNG_IMAGE_FLAG_COLORSPACE_NOT_sRGB))
-         png_set_cHRM_fixed(png_ptr, info_ptr,
-            /* color      x       y */
-            /* white */ 31270, 32900,
-            /* red   */ 64000, 33000,
-            /* green */ 30000, 60000,
-            /* blue  */ 15000,  6000
-         );
-   }
-
-   else if (!(image->flags & PNG_IMAGE_FLAG_COLORSPACE_NOT_sRGB))
-      png_set_sRGB(png_ptr, info_ptr, PNG_sRGB_INTENT_PERCEPTUAL);
-
-   /* Else writing an 8-bit file and the *colors* aren't sRGB, but the 8-bit
-    * space must still be gamma encoded.
-    */
-   else
-      png_set_gAMA_fixed(png_ptr, info_ptr, PNG_GAMMA_sRGB_INVERSE);
-
-   /* Write the file header. */
-   png_write_info(png_ptr, info_ptr);
-
-   /* Now set up the data transformations (*after* the header is written),
-    * remove the handled transformations from the 'format' flags for checking.
-    *
-    * First check for a little endian system if writing 16 bit files.
-    */
-   if (write_16bit)
-   {
-      PNG_CONST png_uint_16 le = 0x0001;
-
-      if (*(png_const_bytep)&le)
-         png_set_swap(png_ptr);
-   }
-
-#  ifdef PNG_SIMPLIFIED_WRITE_BGR_SUPPORTED
-      if (format & PNG_FORMAT_FLAG_BGR)
-      {
-         if (!colormap && (format & PNG_FORMAT_FLAG_COLOR) != 0)
-            png_set_bgr(png_ptr);
-         format &= ~PNG_FORMAT_FLAG_BGR;
-      }
-#  endif
-
-#  ifdef PNG_SIMPLIFIED_WRITE_AFIRST_SUPPORTED
-      if (format & PNG_FORMAT_FLAG_AFIRST)
-      {
-         if (!colormap && (format & PNG_FORMAT_FLAG_ALPHA) != 0)
-            png_set_swap_alpha(png_ptr);
-         format &= ~PNG_FORMAT_FLAG_AFIRST;
-      }
-#  endif
-
-   /* If there are 16 or fewer color-map entries we wrote a lower bit depth
-    * above, but the application data is still byte packed.
-    */
-   if (colormap && image->colormap_entries <= 16)
-      png_set_packing(png_ptr);
-
-   /* That should have handled all (both) the transforms. */
-   if ((format & ~(png_uint_32)(PNG_FORMAT_FLAG_COLOR | PNG_FORMAT_FLAG_LINEAR |
-         PNG_FORMAT_FLAG_ALPHA | PNG_FORMAT_FLAG_COLORMAP)) != 0)
-      png_error(png_ptr, "png_write_image: unsupported transformation");
-
-   {
-      png_const_bytep row = png_voidcast(png_const_bytep, display->buffer);
-      ptrdiff_t row_bytes = display->row_stride;
-
-      if (linear)
-         row_bytes *= (sizeof (png_uint_16));
-
-      if (row_bytes < 0)
-         row += (image->height-1) * (-row_bytes);
-
-      display->first_row = row;
-      display->row_bytes = row_bytes;
-   }
-
-   /* Apply 'fast' options if the flag is set. */
-   if ((image->flags & PNG_IMAGE_FLAG_FAST) != 0)
-   {
-      png_set_filter(png_ptr, PNG_FILTER_TYPE_BASE, PNG_NO_FILTERS);
-      /* NOTE: determined by experiment using pngstest, this reflects some
-       * balance between the time to write the image once and the time to read
-       * it about 50 times.  The speed-up in pngstest was about 10-20% of the
-       * total (user) time on a heavily loaded system.
-       */
-      png_set_compression_level(png_ptr, 3);
-   }
-
-   /* Check for the cases that currently require a pre-transform on the row
-    * before it is written.  This only applies when the input is 16-bit and
-    * either there is an alpha channel or it is converted to 8-bit.
-    */
-   if ((linear && alpha) || (!colormap && display->convert_to_8bit))
-   {
-      png_bytep row = png_voidcast(png_bytep, png_malloc(png_ptr,
-         png_get_rowbytes(png_ptr, info_ptr)));
-      int result;
-
-      display->local_row = row;
-      if (write_16bit)
-         result = png_safe_execute(image, png_write_image_16bit, display);
-      else
-         result = png_safe_execute(image, png_write_image_8bit, display);
-      display->local_row = NULL;
-
-      png_free(png_ptr, row);
-
-      /* Skip the 'write_end' on error: */
-      if (!result)
-         return 0;
-   }
-
-   /* Otherwise this is the case where the input is in a format currently
-    * supported by the rest of the libpng write code; call it directly.
-    */
-   else
-   {
-      png_const_bytep row = png_voidcast(png_const_bytep, display->first_row);
-      ptrdiff_t row_bytes = display->row_bytes;
-      png_uint_32 y = image->height;
-
-      while (y-- > 0)
-      {
-         png_write_row(png_ptr, row);
-         row += row_bytes;
-      }
-   }
-
-   png_write_end(png_ptr, info_ptr);
-   return 1;
-}
-
-int PNGAPI
-png_image_write_to_stdio(png_imagep image, FILE *file, int convert_to_8bit,
-   const void *buffer, png_int_32 row_stride, const void *colormap)
-{
-   /* Write the image to the given (FILE*). */
-   if (image != NULL && image->version == PNG_IMAGE_VERSION)
-   {
-      if (file != NULL)
-      {
-         if (png_image_write_init(image))
-         {
-            png_image_write_control display;
-            int result;
-
-            /* This is slightly evil, but png_init_io doesn't do anything other
-             * than this and we haven't changed the standard IO functions so
-             * this saves a 'safe' function.
-             */
-            image->opaque->png_ptr->io_ptr = file;
-
-            memset(&display, 0, (sizeof display));
-            display.image = image;
-            display.buffer = buffer;
-            display.row_stride = row_stride;
-            display.colormap = colormap;
-            display.convert_to_8bit = convert_to_8bit;
-
-            result = png_safe_execute(image, png_image_write_main, &display);
-            png_image_free(image);
-            return result;
-         }
-
-         else
-            return 0;
-      }
-
-      else
-         return png_image_error(image,
-            "png_image_write_to_stdio: invalid argument");
-   }
-
-   else if (image != NULL)
-      return png_image_error(image,
-         "png_image_write_to_stdio: incorrect PNG_IMAGE_VERSION");
-
-   else
-      return 0;
-}
-
-int PNGAPI
-png_image_write_to_file(png_imagep image, const char *file_name,
-   int convert_to_8bit, const void *buffer, png_int_32 row_stride,
-   const void *colormap)
-{
-   /* Write the image to the named file. */
-   if (image != NULL && image->version == PNG_IMAGE_VERSION)
-   {
-      if (file_name != NULL)
-      {
-         FILE *fp = fopen(file_name, "wb");
-
-         if (fp != NULL)
-         {
-            if (png_image_write_to_stdio(image, fp, convert_to_8bit, buffer,
-               row_stride, colormap))
-            {
-               int error; /* from fflush/fclose */
-
-               /* Make sure the file is flushed correctly. */
-               if (fflush(fp) == 0 && ferror(fp) == 0)
-               {
-                  if (fclose(fp) == 0)
-                     return 1;
-
-                  error = errno; /* from fclose */
-               }
-
-               else
-               {
-                  error = errno; /* from fflush or ferror */
-                  (void)fclose(fp);
-               }
-
-               (void)remove(file_name);
-               /* The image has already been cleaned up; this is just used to
-                * set the error (because the original write succeeded).
-                */
-               return png_image_error(image, strerror(error));
-            }
-
-            else
-            {
-               /* Clean up: just the opened file. */
-               (void)fclose(fp);
-               (void)remove(file_name);
-               return 0;
-            }
-         }
-
-         else
-            return png_image_error(image, strerror(errno));
-      }
-
-      else
-         return png_image_error(image,
-            "png_image_write_to_file: invalid argument");
-   }
-
-   else if (image != NULL)
-      return png_image_error(image,
-         "png_image_write_to_file: incorrect PNG_IMAGE_VERSION");
-
-   else
-      return 0;
-}
-#endif /* PNG_STDIO_SUPPORTED */
-#endif /* SIMPLIFIED_WRITE */
-#endif /* PNG_WRITE_SUPPORTED */