UXP/media/libpng/pngwrite.c

/* pngwrite.c - general routines to write a PNG file
 *
 * Last changed in libpng 1.6.26 [October 20, 2016]
 * Copyright (c) 1998-2002,2004,2006-2016 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"
#ifdef PNG_SIMPLIFIED_WRITE_STDIO_SUPPORTED
#  include <errno.h>
#endif /* SIMPLIFIED_WRITE_STDIO */

#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 != 0)
   {
      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) != 0)
      {
         /* 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 /* WRITE_UNKNOWN_CHUNKS */

/* 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) == 0)
   {
      /* Write PNG signature */
      png_write_sig(png_ptr);

#ifdef PNG_MNG_FEATURES_SUPPORTED
      if ((png_ptr->mode & PNG_HAVE_PNG_SIGNATURE) != 0 && \
          png_ptr->mng_features_permitted != 0)
      {
         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
       * an 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_WRITE_APNG_SUPPORTED
   if ((info_ptr->valid & PNG_INFO_acTL) != 0)
      png_write_acTL(png_ptr, info_ptr->num_frames, info_ptr->num_plays);
#endif
#ifdef PNG_GAMMA_SUPPORTED
#  ifdef PNG_WRITE_gAMA_SUPPORTED
      if ((info_ptr->colorspace.flags & PNG_COLORSPACE_INVALID) == 0 &&
          (info_ptr->colorspace.flags & PNG_COLORSPACE_FROM_gAMA) != 0 &&
          (info_ptr->valid & PNG_INFO_gAMA) != 0)
         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) == 0 &&
             (info_ptr->valid & PNG_INFO_iCCP) != 0)
         {
#    ifdef PNG_WRITE_sRGB_SUPPORTED
               if ((info_ptr->valid & PNG_INFO_sRGB) != 0)
                  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) == 0 &&
             (info_ptr->valid & PNG_INFO_sRGB) != 0)
            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) != 0)
            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) == 0 &&
             (info_ptr->colorspace.flags & PNG_COLORSPACE_FROM_cHRM) != 0 &&
             (info_ptr->valid & PNG_INFO_cHRM) != 0)
            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) != 0)
      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) !=0)
   {
#ifdef PNG_WRITE_INVERT_ALPHA_SUPPORTED
      /* Invert the alpha channel (in tRNS) */
      if ((png_ptr->transformations & PNG_INVERT_ALPHA) != 0 &&
          info_ptr->color_type == PNG_COLOR_TYPE_PALETTE)
      {
         int j, jend;

         jend = info_ptr->num_trans;
         if (jend > PNG_MAX_PALETTE_LENGTH)
            jend = PNG_MAX_PALETTE_LENGTH;

         for (j = 0; j<jend; ++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) != 0)
      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) != 0)
      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) != 0)
      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) != 0)
      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) != 0)
      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) != 0)
      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) != 0)
   {
      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) != 0)
      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);
         /* Mark this chunk as written */
         if (info_ptr->text[i].compression == PNG_TEXT_COMPRESSION_NONE)
            info_ptr->text[i].compression = PNG_TEXT_COMPRESSION_NONE_WR;
         else
            info_ptr->text[i].compression = PNG_TEXT_COMPRESSION_zTXt_WR;
#else
         png_warning(png_ptr, "Unable to write international text");
#endif
      }

      /* 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, info_ptr->text[i].compression);
         /* Mark this chunk as written */
         info_ptr->text[i].compression = PNG_TEXT_COMPRESSION_zTXt_WR;
#else
         png_warning(png_ptr, "Unable to write compressed text");
#endif
      }

      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) == 0)
      png_error(png_ptr, "No IDATs written into file");

#ifdef PNG_WRITE_APNG_SUPPORTED
   if (png_ptr->num_frames_written != png_ptr->num_frames_to_write)
      png_error(png_ptr, "Not enough frames written");
#endif

#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) != 0 &&
          (png_ptr->mode & PNG_WROTE_tIME) == 0)
         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);
            /* Mark this chunk as written */
            if (info_ptr->text[i].compression == PNG_TEXT_COMPRESSION_NONE)
               info_ptr->text[i].compression = PNG_TEXT_COMPRESSION_NONE_WR;
            else
               info_ptr->text[i].compression = PNG_TEXT_COMPRESSION_zTXt_WR;
#else
            png_warning(png_ptr, "Unable to write international text");
#endif
         }

         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, info_ptr->text[i].compression);
            /* Mark this chunk as written */
            info_ptr->text[i].compression = PNG_TEXT_COMPRESSION_zTXt_WR;
#else
            png_warning(png_ptr, "Unable to write compressed text");
#endif
         }

         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
            png_warning(png_ptr, "Unable to write uncompressed text");
#endif
         }
      }
#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 /* USER_MEM */
   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 /* WRITE_COMPRESSED_TEXT */

      /* 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
      /* In stable builds only warn if an application error can be completely
       * handled.
       */
      png_ptr->flags |= PNG_FLAG_BENIGN_ERRORS_WARN;
#endif

      /* App warnings are warnings in release (or release candidate) builds but
       * are errors during development.
       */
#if PNG_RELEASE_BUILD
      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);
      }
   }
}

#ifdef PNG_MNG_FEATURES_SUPPORTED
/* Performs intrapixel differencing  */
static void
png_do_write_intrapixel(png_row_infop row_info, png_bytep row)
{
   png_debug(1, "in png_do_write_intrapixel");

   if ((row_info->color_type & PNG_COLOR_MASK_COLOR) != 0)
   {
      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)(*rp       - *(rp + 1));
            *(rp + 2) = (png_byte)(*(rp + 2) - *(rp + 1));
         }
      }

#ifdef PNG_WRITE_16BIT_SUPPORTED
      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   = (png_uint_32)(*(rp    ) << 8) | *(rp + 1);
            png_uint_32 s1   = (png_uint_32)(*(rp + 2) << 8) | *(rp + 3);
            png_uint_32 s2   = (png_uint_32)(*(rp + 4) << 8) | *(rp + 5);
            png_uint_32 red  = (png_uint_32)((s0 - s1) & 0xffffL);
            png_uint_32 blue = (png_uint_32)((s2 - s1) & 0xffffL);
            *(rp    ) = (png_byte)(red >> 8);
            *(rp + 1) = (png_byte)red;
            *(rp + 4) = (png_byte)(blue >> 8);
            *(rp + 5) = (png_byte)blue;
         }
      }
#endif /* WRITE_16BIT */
   }
}
#endif /* MNG_FEATURES */

/* 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) == 0)
         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) != 0)
         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) != 0)
         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) != 0)
         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) != 0)
         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) != 0)
         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) != 0)
         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) != 0)
         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 != 0 &&
       (png_ptr->transformations & PNG_INTERLACE) != 0)
   {
      switch (png_ptr->pass)
      {
         case 0:
            if ((png_ptr->row_number & 0x07) != 0)
            {
               png_write_finish_row(png_ptr);
               return;
            }
            break;

         case 1:
            if ((png_ptr->row_number & 0x07) != 0 || 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) != 0 || 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) != 0 || png_ptr->width < 2)
            {
               png_write_finish_row(png_ptr);
               return;
            }
            break;

         case 6:
            if ((png_ptr->row_number & 0x01) == 0)
            {
               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) != 0)
   {
      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 == 0)
      {
         png_write_finish_row(png_ptr);
         return;
      }
   }
#endif

#ifdef PNG_WRITE_TRANSFORMS_SUPPORTED
   /* Handle other transformations */
   if (png_ptr->transformations != 0)
      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) != 0 &&
       (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 : (png_uint_32)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 /* WRITE_FLUSH */

/* 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) != 0)
      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);
   png_ptr->row_buf = NULL;
#ifdef PNG_WRITE_FILTER_SUPPORTED
   png_free(png_ptr, png_ptr->prev_row);
   png_free(png_ptr, png_ptr->try_row);
   png_free(png_ptr, png_ptr->tst_row);
   png_ptr->prev_row = NULL;
   png_ptr->try_row = NULL;
   png_ptr->tst_row = NULL;
#endif

#ifdef PNG_SET_UNKNOWN_CHUNKS_SUPPORTED
   png_free(png_ptr, png_ptr->chunk_list);
   png_ptr->chunk_list = NULL;
#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) != 0 &&
       (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 /* WRITE_FILTER */
         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 /* WRITE_FILTER */
      }

#ifdef 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 remove them
       * or add them back after the start of compression.
       *
       * NOTE: this is a nasty constraint on the code, because it means that the
       * prev_row buffer must be maintained even if there are currently no
       * 'prev_row' requiring filters active.
       */
      if (png_ptr->row_buf != NULL)
      {
         int num_filters;
         png_alloc_size_t buf_size;

         /* Repeat the checks in png_write_start_row; 1 pixel high or wide
          * images cannot benefit from certain filters.  If this isn't done here
          * the check below will fire on 1 pixel high images.
          */
         if (png_ptr->height == 1)
            filters &= ~(PNG_FILTER_UP|PNG_FILTER_AVG|PNG_FILTER_PAETH);

         if (png_ptr->width == 1)
            filters &= ~(PNG_FILTER_SUB|PNG_FILTER_AVG|PNG_FILTER_PAETH);

         if ((filters & (PNG_FILTER_UP|PNG_FILTER_AVG|PNG_FILTER_PAETH)) != 0
            && png_ptr->prev_row == NULL)
         {
            /* This is the error case, however it is benign - the previous row
             * is not available so the filter can't be used.  Just warn here.
             */
            png_app_warning(png_ptr,
                "png_set_filter: UP/AVG/PAETH cannot be added after start");
            filters &= ~(PNG_FILTER_UP|PNG_FILTER_AVG|PNG_FILTER_PAETH);
         }

         num_filters = 0;

         if (filters & PNG_FILTER_SUB)
            num_filters++;

         if (filters & PNG_FILTER_UP)
            num_filters++;

         if (filters & PNG_FILTER_AVG)
            num_filters++;

         if (filters & PNG_FILTER_PAETH)
            num_filters++;

         /* Allocate needed row buffers if they have not already been