pngrutil.c

一个国人自己实现图像库的程序（有参考价值）

   }

   png_crc_read(png_ptr, buf, 1);
   if (png_crc_finish(png_ptr, 0))
      return;

   intent = buf[0];
   /* check for bad intent */
   if (intent >= PNG_sRGB_INTENT_LAST)
   {
      png_warning(png_ptr, "Unknown sRGB intent");
      return;
   }

#if defined(PNG_READ_gAMA_SUPPORTED) && defined(PNG_READ_GAMMA_SUPPORTED)
   if ((info_ptr->valid & PNG_INFO_gAMA))
   {
   int igamma;
#ifdef PNG_FIXED_POINT_SUPPORTED
      igamma=(int)info_ptr->int_gamma;
#else
#  ifdef PNG_FLOATING_POINT_SUPPORTED
      igamma=(int)(info_ptr->gamma * 100000.);
#  endif
#endif
#if 0 && defined(PNG_cHRM_SUPPORTED) && !defined(PNG_FIXED_POINT_SUPPORTED)
/* We need to define these here because they aren't in png.h */
   png_fixed_point int_x_white;
   png_fixed_point int_y_white;
   png_fixed_point int_x_red;
   png_fixed_point int_y_red;
   png_fixed_point int_x_green;
   png_fixed_point int_y_green;
   png_fixed_point int_x_blue;
   png_fixed_point int_y_blue;
#endif
      if(igamma < 45000L || igamma > 46000L)
      {
         png_warning(png_ptr,
           "Ignoring incorrect gAMA value when sRGB is also present");
#ifndef PNG_NO_CONSOLE_IO
#  ifdef PNG_FIXED_POINT_SUPPORTED
         fprintf(stderr,"incorrect gamma=(%d/100000)\n",(int)png_ptr->int_gamma);
#  else
#    ifdef PNG_FLOATING_POINT_SUPPORTED
         fprintf(stderr,"incorrect gamma=%f\n",png_ptr->gamma);
#    endif
#  endif
#endif
      }
   }
#endif /* PNG_READ_gAMA_SUPPORTED */

#ifdef PNG_READ_cHRM_SUPPORTED
#ifdef PNG_FIXED_POINT_SUPPORTED
   if (info_ptr->valid & PNG_INFO_cHRM)
      if (abs(info_ptr->int_x_white - 31270L) > 1000 ||
          abs(info_ptr->int_y_white - 32900L) > 1000 ||
          abs(info_ptr->int_x_red   - 64000L) > 1000 ||
          abs(info_ptr->int_y_red   - 33000L) > 1000 ||
          abs(info_ptr->int_x_green - 30000L) > 1000 ||
          abs(info_ptr->int_y_green - 60000L) > 1000 ||
          abs(info_ptr->int_x_blue  - 15000L) > 1000 ||
          abs(info_ptr->int_y_blue  -  6000L) > 1000)
         {
            png_warning(png_ptr,
              "Ignoring incorrect cHRM value when sRGB is also present");
         }
#endif /* PNG_FIXED_POINT_SUPPORTED */
#endif /* PNG_READ_cHRM_SUPPORTED */

   png_set_sRGB_gAMA_and_cHRM(png_ptr, info_ptr, intent);
}
#endif /* PNG_READ_sRGB_SUPPORTED */

#if defined(PNG_READ_iCCP_SUPPORTED)
void /* PRIVATE */
png_handle_iCCP(png_structp png_ptr, png_infop info_ptr, png_uint_32 length)
/* Note: this does not properly handle chunks that are > 64K under DOS */
{
   png_charp chunkdata;
   png_byte compression_type;
   png_charp profile;
   png_uint_32 skip = 0;
   png_uint_32 profile_size = 0;
   png_uint_32 profile_length = 0;
   png_size_t slength, prefix_length, data_length;

   png_debug(1, "in png_handle_iCCP\n");

   if (!(png_ptr->mode & PNG_HAVE_IHDR))
      png_error(png_ptr, "Missing IHDR before iCCP");
   else if (png_ptr->mode & PNG_HAVE_IDAT)
   {
      png_warning(png_ptr, "Invalid iCCP after IDAT");
      png_crc_finish(png_ptr, length);
      return;
   }
   else if (png_ptr->mode & PNG_HAVE_PLTE)
      /* Should be an error, but we can cope with it */
      png_warning(png_ptr, "Out of place iCCP chunk");

   else if (info_ptr != NULL && (info_ptr->valid & PNG_INFO_iCCP))
   {
      png_warning(png_ptr, "Duplicate iCCP chunk");
      png_crc_finish(png_ptr, length);
      return;
   }

#ifdef PNG_MAX_MALLOC_64K
   if (length > (png_uint_32)65535L)
   {
      png_warning(png_ptr, "iCCP chunk too large to fit in memory");
      skip = length - (png_uint_32)65535L;
      length = (png_uint_32)65535L;
   }
#endif

   chunkdata = (png_charp)png_malloc(png_ptr, length + 1);
   slength = (png_size_t)length;
   png_crc_read(png_ptr, (png_bytep)chunkdata, slength);

   if (png_crc_finish(png_ptr, skip))
   {
      png_free(png_ptr, chunkdata);
      return;
   }

   chunkdata[slength] = 0x00;

   for (profile = chunkdata; *profile; profile++)
      /* empty loop to find end of name */ ;

   ++profile;

   /* there should be at least one zero (the compression type byte)
      following the separator, and we should be on it  */
   if ( profile >= chunkdata + slength)
   {
      png_free(png_ptr, chunkdata);
      png_warning(png_ptr, "Malformed iCCP chunk");
      return;
   }

   /* compression_type should always be zero */
   compression_type = *profile++;
   if (compression_type)
   {
      png_warning(png_ptr, "Ignoring nonzero compression type in iCCP chunk");
      compression_type=0x00;  /* Reset it to zero (libpng-1.0.6 through 1.0.8
                                 wrote nonzero) */
   }

   prefix_length = profile - chunkdata;
   chunkdata = png_decompress_chunk(png_ptr, compression_type, chunkdata,
                                    slength, prefix_length, &data_length);

   profile_length = data_length - prefix_length;

   if ( prefix_length > data_length || profile_length < 4)
   {
      png_free(png_ptr, chunkdata);
      png_warning(png_ptr, "Profile size field missing from iCCP chunk");
      return;
   }

   /* Check the profile_size recorded in the first 32 bits of the ICC profile */
   profile_size = ((*(chunkdata+prefix_length))<<24) |
                  ((*(chunkdata+prefix_length+1))<<16) |
                  ((*(chunkdata+prefix_length+2))<< 8) |
                  ((*(chunkdata+prefix_length+3))    );

   if(profile_size < profile_length)
      profile_length = profile_size;

   if(profile_size > profile_length)
   {
      png_free(png_ptr, chunkdata);
      png_warning(png_ptr, "Ignoring truncated iCCP profile.\n");
      return;
   }

   png_set_iCCP(png_ptr, info_ptr, chunkdata, compression_type,
                chunkdata + prefix_length, profile_length);
   png_free(png_ptr, chunkdata);
}
#endif /* PNG_READ_iCCP_SUPPORTED */

#if defined(PNG_READ_sPLT_SUPPORTED)
void /* PRIVATE */
png_handle_sPLT(png_structp png_ptr, png_infop info_ptr, png_uint_32 length)
/* Note: this does not properly handle chunks that are > 64K under DOS */
{
   png_bytep chunkdata;
   png_bytep entry_start;
   png_sPLT_t new_palette;
#ifdef PNG_NO_POINTER_INDEXING
   png_sPLT_entryp pp;
#endif
   int data_length, entry_size, i;
   png_uint_32 skip = 0;
   png_size_t slength;

   png_debug(1, "in png_handle_sPLT\n");

   if (!(png_ptr->mode & PNG_HAVE_IHDR))
      png_error(png_ptr, "Missing IHDR before sPLT");
   else if (png_ptr->mode & PNG_HAVE_IDAT)
   {
      png_warning(png_ptr, "Invalid sPLT after IDAT");
      png_crc_finish(png_ptr, length);
      return;
   }

#ifdef PNG_MAX_MALLOC_64K
   if (length > (png_uint_32)65535L)
   {
      png_warning(png_ptr, "sPLT chunk too large to fit in memory");
      skip = length - (png_uint_32)65535L;
      length = (png_uint_32)65535L;
   }
#endif

   chunkdata = (png_bytep)png_malloc(png_ptr, length + 1);
   slength = (png_size_t)length;
   png_crc_read(png_ptr, (png_bytep)chunkdata, slength);

   if (png_crc_finish(png_ptr, skip))
   {
      png_free(png_ptr, chunkdata);
      return;
   }

   chunkdata[slength] = 0x00;

   for (entry_start = chunkdata; *entry_start; entry_start++)
      /* empty loop to find end of name */ ;
   ++entry_start;

   /* a sample depth should follow the separator, and we should be on it  */
   if (entry_start > chunkdata + slength)
   {
      png_free(png_ptr, chunkdata);
      png_warning(png_ptr, "malformed sPLT chunk");
      return;
   }

   new_palette.depth = *entry_start++;
   entry_size = (new_palette.depth == 8 ? 6 : 10);
   data_length = (slength - (entry_start - chunkdata));

   /* integrity-check the data length */
   if (data_length % entry_size)
   {
      png_free(png_ptr, chunkdata);
      png_warning(png_ptr, "sPLT chunk has bad length");
      return;
   }

   new_palette.nentries = data_length / entry_size;
   new_palette.entries = (png_sPLT_entryp)png_malloc(
       png_ptr, new_palette.nentries * sizeof(png_sPLT_entry));

#ifndef PNG_NO_POINTER_INDEXING
   for (i = 0; i < new_palette.nentries; i++)
   {
      png_sPLT_entryp pp = new_palette.entries + i;

      if (new_palette.depth == 8)
      {
          pp->red = *entry_start++;
          pp->green = *entry_start++;
          pp->blue = *entry_start++;
          pp->alpha = *entry_start++;
      }
      else
      {
          pp->red   = png_get_uint_16(entry_start); entry_start += 2;
          pp->green = png_get_uint_16(entry_start); entry_start += 2;
          pp->blue  = png_get_uint_16(entry_start); entry_start += 2;
          pp->alpha = png_get_uint_16(entry_start); entry_start += 2;
      }
      pp->frequency = png_get_uint_16(entry_start); entry_start += 2;
   }
#else
   pp = new_palette.entries;
   for (i = 0; i < new_palette.nentries; i++)
   {

      if (new_palette.depth == 8)
      {
          pp[i].red   = *entry_start++;
          pp[i].green = *entry_start++;
          pp[i].blue  = *entry_start++;
          pp[i].alpha = *entry_start++;
      }
      else
      {
          pp[i].red   = png_get_uint_16(entry_start); entry_start += 2;
          pp[i].green = png_get_uint_16(entry_start); entry_start += 2;
          pp[i].blue  = png_get_uint_16(entry_start); entry_start += 2;
          pp[i].alpha = png_get_uint_16(entry_start); entry_start += 2;
      }
      pp->frequency = png_get_uint_16(entry_start); entry_start += 2;
   }
#endif

   /* discard all chunk data except the name and stash that */
   new_palette.name = (png_charp)chunkdata;

   png_set_sPLT(png_ptr, info_ptr, &new_palette, 1);

   png_free(png_ptr, chunkdata);
   png_free(png_ptr, new_palette.entries);
}
#endif /* PNG_READ_sPLT_SUPPORTED */

#if defined(PNG_READ_tRNS_SUPPORTED)
void /* PRIVATE */
png_handle_tRNS(png_structp png_ptr, png_infop info_ptr, png_uint_32 length)
{
   png_byte	readbuf[PNG_MAX_PALETTE_LENGTH];

   png_debug(1, "in png_handle_tRNS\n");

   if (!(png_ptr->mode & PNG_HAVE_IHDR))
      png_error(png_ptr, "Missing IHDR before tRNS");
   else if (png_ptr->mode & PNG_HAVE_IDAT)
   {
      png_warning(png_ptr, "Invalid tRNS after IDAT");
      png_crc_finish(png_ptr, length);
      return;
   }
   else if (info_ptr != NULL && (info_ptr->valid & PNG_INFO_tRNS))
   {
      png_warning(png_ptr, "Duplicate tRNS chunk");
      png_crc_finish(png_ptr, length);
      return;
   }

   if (png_ptr->color_type == PNG_COLOR_TYPE_PALETTE)
   {
      if (!(png_ptr->mode & PNG_HAVE_PLTE))
      {
         /* Should be an error, but we can cope with it */
         png_warning(png_ptr, "Missing PLTE before tRNS");
      }
      else if (length > (png_uint_32)png_ptr->num_palette)
      {
         png_warning(png_ptr, "Incorrect tRNS chunk length");
         png_crc_finish(png_ptr, length);
         return;
      }
      if (length == 0)
      {
         png_warning(png_ptr, "Zero length tRNS chunk");
         png_crc_finish(png_ptr, length);
         return;
      }

      png_crc_read(png_ptr, readbuf, (png_size_t)length);
      png_ptr->num_trans = (png_uint_16)length;
   }
   else if (png_ptr->color_type == PNG_COLOR_TYPE_RGB)
   {
      png_byte buf[6];

      if (length != 6)
      {
         png_warning(png_ptr, "Incorrect tRNS chunk length");
         png_crc_finish(png_ptr, length);
         return;
      }

      png_crc_read(png_ptr, buf, (png_size_t)length);
      png_ptr->num_trans = 1;
      png_ptr->trans_values.red = png_get_uint_16(buf);
      png_ptr->trans_values.green = png_get_uint_16(buf + 2);
      png_ptr->trans_values.blue = png_get_uint_16(buf + 4);
   }
   else if (png_ptr->color_type == PNG_COLOR_TYPE_GRAY)
   {
      png_byte buf[6];

      if (length != 2)
      {
         png_warning(png_ptr, "Incorrect tRNS chunk length");
         png_crc_finish(png_ptr, length);
         return;
      }

      png_crc_read(png_ptr, buf, 2);
      png_ptr->num_trans = 1;
      png_ptr->trans_values.gray = png_get_uint_16(buf);
   }
   else
   {
      png_warning(png_ptr, "tRNS chunk not allowed with alpha channel");
      png_crc_finish(png_ptr, length);
      return;
   }

   if (png_crc_finish(png_ptr, 0))
      return;

   png_set_tRNS(png_ptr, info_ptr, readbuf, png_ptr->num_trans,
      &(png_ptr->trans_values));
}
#endif

#if defined(PNG_READ_bKGD_SUPPORTED)
void /* PRIVATE */
png_handle_bKGD(png_structp png_ptr, png_infop info_ptr, png_uint_32 length)
{
   png_size_t truelen;
   png_byte buf[6];

   png_debug(1, "in png_handle_bKGD\n");

   if (!(png_ptr->mode & PNG_HAVE_IHDR))
      png_error(png_ptr, "Missing IHDR before bKGD");
   else if (png_ptr->mode & PNG_HAVE_IDAT)
   {
      png_warning(png_ptr, "Invalid bKGD after IDAT");
      png_crc_finish(png_ptr, length);
      return;
   }
   else if (png_ptr->color_type == PNG_COLOR_TYPE_PALETTE &&
            !(png_ptr->mode & PNG_HAVE_PLTE))
   {
      png_warning(png_ptr, "Missing PLTE before bKGD");
      png_crc_finish(png_ptr, length);
      return;
   }
   else if (info_ptr != NULL && (info_ptr->valid & PNG_INFO_bKGD))
   {