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src/Source/LibPNG/pngtrans.c  view on Meta::CPAN

   {
#     ifdef PNG_READ_FILLER_SUPPORTED
         /* On read png_set_filler is always valid, regardless of the base PNG
          * format, because other transformations can give a format where the
          * filler code can execute (basically an 8 or 16-bit component RGB or G
          * format.)
          *
          * NOTE: usr_channels is not used by the read code!  (This has led to
          * confusion in the past.)  The filler is only used in the read code.
          */
         png_ptr->filler = (png_uint_16)filler;
#     else
         png_app_error(png_ptr, "png_set_filler not supported on read");
         PNG_UNUSED(filler) /* not used in the write case */
         return;
#     endif
   }

   else /* write */
   {
#     ifdef PNG_WRITE_FILLER_SUPPORTED
         /* On write the usr_channels parameter must be set correctly at the
          * start to record the number of channels in the app-supplied data.
          */
         switch (png_ptr->color_type)
         {
            case PNG_COLOR_TYPE_RGB:
               png_ptr->usr_channels = 4;
               break;

            case PNG_COLOR_TYPE_GRAY:
               if (png_ptr->bit_depth >= 8)
               {
                  png_ptr->usr_channels = 2;
                  break;
               }

               else
               {
                  /* There simply isn't any code in libpng to strip out bits
                   * from bytes when the components are less than a byte in
                   * size!
                   */
                  png_app_error(png_ptr,
                     "png_set_filler is invalid for low bit depth gray output");
                  return;
               }

            default:
               png_app_error(png_ptr,
                  "png_set_filler: inappropriate color type");
               return;
         }
#     else
         png_app_error(png_ptr, "png_set_filler not supported on write");
         return;
#     endif
   }

   /* Here on success - libpng supports the operation, set the transformation
    * and the flag to say where the filler channel is.
    */
   png_ptr->transformations |= PNG_FILLER;

   if (filler_loc == PNG_FILLER_AFTER)
      png_ptr->flags |= PNG_FLAG_FILLER_AFTER;

   else
      png_ptr->flags &= ~PNG_FLAG_FILLER_AFTER;
}

/* Added to libpng-1.2.7 */
void PNGAPI
png_set_add_alpha(png_structrp png_ptr, png_uint_32 filler, int filler_loc)
{
   png_debug(1, "in png_set_add_alpha");

   if (png_ptr == NULL)
      return;

   png_set_filler(png_ptr, filler, filler_loc);
   /* The above may fail to do anything. */
   if ((png_ptr->transformations & PNG_FILLER) != 0)
      png_ptr->transformations |= PNG_ADD_ALPHA;
}

#endif

#if defined(PNG_READ_SWAP_ALPHA_SUPPORTED) || \
    defined(PNG_WRITE_SWAP_ALPHA_SUPPORTED)
void PNGAPI
png_set_swap_alpha(png_structrp png_ptr)
{
   png_debug(1, "in png_set_swap_alpha");

   if (png_ptr == NULL)
      return;

   png_ptr->transformations |= PNG_SWAP_ALPHA;
}
#endif

#if defined(PNG_READ_INVERT_ALPHA_SUPPORTED) || \
    defined(PNG_WRITE_INVERT_ALPHA_SUPPORTED)
void PNGAPI
png_set_invert_alpha(png_structrp png_ptr)
{
   png_debug(1, "in png_set_invert_alpha");

   if (png_ptr == NULL)
      return;

   png_ptr->transformations |= PNG_INVERT_ALPHA;
}
#endif

#if defined(PNG_READ_INVERT_SUPPORTED) || defined(PNG_WRITE_INVERT_SUPPORTED)
void PNGAPI
png_set_invert_mono(png_structrp png_ptr)
{
   png_debug(1, "in png_set_invert_mono");