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

   /* New in libpng-1.5.4 - reserve particular negative values as flags. */
   scrn_gamma = translate_gamma_flags(png_ptr, scrn_gamma, 1/*screen*/);
   file_gamma = translate_gamma_flags(png_ptr, file_gamma, 0/*file*/);

   /* Checking the gamma values for being >0 was added in 1.5.4 along with the
    * premultiplied alpha support; this actually hides an undocumented feature
    * of the previous implementation which allowed gamma processing to be
    * disabled in background handling.  There is no evidence (so far) that this
    * was being used; however, png_set_background itself accepted and must still
    * accept '0' for the gamma value it takes, because it isn't always used.
    *
    * Since this is an API change (albeit a very minor one that removes an
    * undocumented API feature) the following checks were only enabled in
    * libpng-1.6.0.
    */
   if (file_gamma <= 0)
      png_error(png_ptr, "invalid file gamma in png_set_gamma");

   if (scrn_gamma <= 0)
      png_error(png_ptr, "invalid screen gamma in png_set_gamma");

   /* Set the gamma values unconditionally - this overrides the value in the PNG
    * file if a gAMA chunk was present.  png_set_alpha_mode provides a
    * different, easier, way to default the file gamma.
    */
   png_ptr->colorspace.gamma = file_gamma;
   png_ptr->colorspace.flags |= PNG_COLORSPACE_HAVE_GAMMA;
   png_ptr->screen_gamma = scrn_gamma;
}

#  ifdef PNG_FLOATING_POINT_SUPPORTED
void PNGAPI
png_set_gamma(png_structrp png_ptr, double scrn_gamma, double file_gamma)
{
   png_set_gamma_fixed(png_ptr, convert_gamma_value(png_ptr, scrn_gamma),
      convert_gamma_value(png_ptr, file_gamma));
}
#  endif /* FLOATING_POINT */
#endif /* READ_GAMMA */

#ifdef PNG_READ_EXPAND_SUPPORTED
/* Expand paletted images to RGB, expand grayscale images of
 * less than 8-bit depth to 8-bit depth, and expand tRNS chunks
 * to alpha channels.
 */
void PNGAPI
png_set_expand(png_structrp png_ptr)
{
   png_debug(1, "in png_set_expand");

   if (png_rtran_ok(png_ptr, 0) == 0)
      return;

   png_ptr->transformations |= (PNG_EXPAND | PNG_EXPAND_tRNS);
}

/* GRR 19990627:  the following three functions currently are identical
 *  to png_set_expand().  However, it is entirely reasonable that someone
 *  might wish to expand an indexed image to RGB but *not* expand a single,
 *  fully transparent palette entry to a full alpha channel--perhaps instead
 *  convert tRNS to the grayscale/RGB format (16-bit RGB value), or replace
 *  the transparent color with a particular RGB value, or drop tRNS entirely.
 *  IOW, a future version of the library may make the transformations flag
 *  a bit more fine-grained, with separate bits for each of these three
 *  functions.
 *
 *  More to the point, these functions make it obvious what libpng will be
 *  doing, whereas "expand" can (and does) mean any number of things.
 *
 *  GRP 20060307: In libpng-1.2.9, png_set_gray_1_2_4_to_8() was modified
 *  to expand only the sample depth but not to expand the tRNS to alpha
 *  and its name was changed to png_set_expand_gray_1_2_4_to_8().
 */

/* Expand paletted images to RGB. */
void PNGAPI
png_set_palette_to_rgb(png_structrp png_ptr)
{
   png_debug(1, "in png_set_palette_to_rgb");

   if (png_rtran_ok(png_ptr, 0) == 0)
      return;

   png_ptr->transformations |= (PNG_EXPAND | PNG_EXPAND_tRNS);
}

/* Expand grayscale images of less than 8-bit depth to 8 bits. */
void PNGAPI
png_set_expand_gray_1_2_4_to_8(png_structrp png_ptr)
{
   png_debug(1, "in png_set_expand_gray_1_2_4_to_8");

   if (png_rtran_ok(png_ptr, 0) == 0)
      return;

   png_ptr->transformations |= PNG_EXPAND;
}

/* Expand tRNS chunks to alpha channels. */
void PNGAPI
png_set_tRNS_to_alpha(png_structrp png_ptr)
{
   png_debug(1, "in png_set_tRNS_to_alpha");

   if (png_rtran_ok(png_ptr, 0) == 0)
      return;

   png_ptr->transformations |= (PNG_EXPAND | PNG_EXPAND_tRNS);
}
#endif /* READ_EXPAND */

#ifdef PNG_READ_EXPAND_16_SUPPORTED
/* Expand to 16-bit channels, expand the tRNS chunk too (because otherwise
 * it may not work correctly.)
 */
void PNGAPI
png_set_expand_16(png_structrp png_ptr)
{
   png_debug(1, "in png_set_expand_16");

   if (png_rtran_ok(png_ptr, 0) == 0)
      return;

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

      png_error(png_ptr, "Uninitialized row");
   }

#ifdef PNG_READ_EXPAND_SUPPORTED
   if ((png_ptr->transformations & PNG_EXPAND) != 0)
   {
      if (row_info->color_type == PNG_COLOR_TYPE_PALETTE)
      {
         png_do_expand_palette(row_info, png_ptr->row_buf + 1,
             png_ptr->palette, png_ptr->trans_alpha, png_ptr->num_trans);
      }

      else
      {
         if (png_ptr->num_trans != 0 &&
             (png_ptr->transformations & PNG_EXPAND_tRNS) != 0)
            png_do_expand(row_info, png_ptr->row_buf + 1,
                &(png_ptr->trans_color));

         else
            png_do_expand(row_info, png_ptr->row_buf + 1,
                NULL);
      }
   }
#endif

#ifdef PNG_READ_STRIP_ALPHA_SUPPORTED
   if ((png_ptr->transformations & PNG_STRIP_ALPHA) != 0 &&
       (png_ptr->transformations & PNG_COMPOSE) == 0 &&
       (row_info->color_type == PNG_COLOR_TYPE_RGB_ALPHA ||
       row_info->color_type == PNG_COLOR_TYPE_GRAY_ALPHA))
      png_do_strip_channel(row_info, png_ptr->row_buf + 1,
         0 /* at_start == false, because SWAP_ALPHA happens later */);
#endif

#ifdef PNG_READ_RGB_TO_GRAY_SUPPORTED
   if ((png_ptr->transformations & PNG_RGB_TO_GRAY) != 0)
   {
      int rgb_error =
          png_do_rgb_to_gray(png_ptr, row_info,
              png_ptr->row_buf + 1);

      if (rgb_error != 0)
      {
         png_ptr->rgb_to_gray_status=1;
         if ((png_ptr->transformations & PNG_RGB_TO_GRAY) ==
             PNG_RGB_TO_GRAY_WARN)
            png_warning(png_ptr, "png_do_rgb_to_gray found nongray pixel");

         if ((png_ptr->transformations & PNG_RGB_TO_GRAY) ==
             PNG_RGB_TO_GRAY_ERR)
            png_error(png_ptr, "png_do_rgb_to_gray found nongray pixel");
      }
   }
#endif

/* From Andreas Dilger e-mail to png-implement, 26 March 1998:
 *
 *   In most cases, the "simple transparency" should be done prior to doing
 *   gray-to-RGB, or you will have to test 3x as many bytes to check if a
 *   pixel is transparent.  You would also need to make sure that the
 *   transparency information is upgraded to RGB.
 *
 *   To summarize, the current flow is:
 *   - Gray + simple transparency -> compare 1 or 2 gray bytes and composite
 *                                   with background "in place" if transparent,
 *                                   convert to RGB if necessary
 *   - Gray + alpha -> composite with gray background and remove alpha bytes,
 *                                   convert to RGB if necessary
 *
 *   To support RGB backgrounds for gray images we need:
 *   - Gray + simple transparency -> convert to RGB + simple transparency,
 *                                   compare 3 or 6 bytes and composite with
 *                                   background "in place" if transparent
 *                                   (3x compare/pixel compared to doing
 *                                   composite with gray bkgrnd)
 *   - Gray + alpha -> convert to RGB + alpha, composite with background and
 *                                   remove alpha bytes (3x float
 *                                   operations/pixel compared with composite
 *                                   on gray background)
 *
 *  Greg's change will do this.  The reason it wasn't done before is for
 *  performance, as this increases the per-pixel operations.  If we would check
 *  in advance if the background was gray or RGB, and position the gray-to-RGB
 *  transform appropriately, then it would save a lot of work/time.
 */

#ifdef PNG_READ_GRAY_TO_RGB_SUPPORTED
   /* If gray -> RGB, do so now only if background is non-gray; else do later
    * for performance reasons
    */
   if ((png_ptr->transformations & PNG_GRAY_TO_RGB) != 0 &&
       (png_ptr->mode & PNG_BACKGROUND_IS_GRAY) == 0)
      png_do_gray_to_rgb(row_info, png_ptr->row_buf + 1);
#endif

#if defined(PNG_READ_BACKGROUND_SUPPORTED) ||\
   defined(PNG_READ_ALPHA_MODE_SUPPORTED)
   if ((png_ptr->transformations & PNG_COMPOSE) != 0)
      png_do_compose(row_info, png_ptr->row_buf + 1, png_ptr);
#endif

#ifdef PNG_READ_GAMMA_SUPPORTED
   if ((png_ptr->transformations & PNG_GAMMA) != 0 &&
#ifdef PNG_READ_RGB_TO_GRAY_SUPPORTED
      /* Because RGB_TO_GRAY does the gamma transform. */
      (png_ptr->transformations & PNG_RGB_TO_GRAY) == 0 &&
#endif
#if defined(PNG_READ_BACKGROUND_SUPPORTED) ||\
   defined(PNG_READ_ALPHA_MODE_SUPPORTED)
      /* Because PNG_COMPOSE does the gamma transform if there is something to
       * do (if there is an alpha channel or transparency.)
       */
       !((png_ptr->transformations & PNG_COMPOSE) &&
       ((png_ptr->num_trans != 0) ||
       (png_ptr->color_type & PNG_COLOR_MASK_ALPHA) != 0)) &&
#endif
      /* Because png_init_read_transformations transforms the palette, unless
       * RGB_TO_GRAY will do the transform.
       */
       (png_ptr->color_type != PNG_COLOR_TYPE_PALETTE))
      png_do_gamma(row_info, png_ptr->row_buf + 1, png_ptr);
#endif

#ifdef PNG_READ_STRIP_ALPHA_SUPPORTED
   if ((png_ptr->transformations & PNG_STRIP_ALPHA) != 0 &&
       (png_ptr->transformations & PNG_COMPOSE) != 0 &&
       (row_info->color_type == PNG_COLOR_TYPE_RGB_ALPHA ||
       row_info->color_type == PNG_COLOR_TYPE_GRAY_ALPHA))
      png_do_strip_channel(row_info, png_ptr->row_buf + 1,
          0 /* at_start == false, because SWAP_ALPHA happens later */);
#endif

#ifdef PNG_READ_ALPHA_MODE_SUPPORTED