pngrtran.c

hl2 source code. Do not use it illegal.

                     palette[i].red = png_ptr->gamma_from_1[w];

                     v = png_ptr->gamma_to_1[palette[i].green];
                     png_composite(w, v, png_ptr->trans[i], back_1.green);
                     palette[i].green = png_ptr->gamma_from_1[w];

                     v = png_ptr->gamma_to_1[palette[i].blue];
                     png_composite(w, v, png_ptr->trans[i], back_1.blue);
                     palette[i].blue = png_ptr->gamma_from_1[w];
                  }
               }
               else
               {
                  palette[i].red = png_ptr->gamma_table[palette[i].red];
                  palette[i].green = png_ptr->gamma_table[palette[i].green];
                  palette[i].blue = png_ptr->gamma_table[palette[i].blue];
               }
            }
         }
         /* if (png_ptr->background_gamma_type!=PNG_BACKGROUND_GAMMA_UNKNOWN)*/
         else
         /* color_type != PNG_COLOR_TYPE_PALETTE */
         {
            double m = (double)(((png_uint_32)1 << png_ptr->bit_depth) - 1);
            double g = 1.0;
            double gs = 1.0;

            switch (png_ptr->background_gamma_type)
            {
               case PNG_BACKGROUND_GAMMA_SCREEN:
                  g = (png_ptr->screen_gamma);
                  gs = 1.0;
                  break;
               case PNG_BACKGROUND_GAMMA_FILE:
                  g = 1.0 / (png_ptr->gamma);
                  gs = 1.0 / (png_ptr->gamma * png_ptr->screen_gamma);
                  break;
               case PNG_BACKGROUND_GAMMA_UNIQUE:
                  g = 1.0 / (png_ptr->background_gamma);
                  gs = 1.0 / (png_ptr->background_gamma *
                     png_ptr->screen_gamma);
                  break;
            }

            if (color_type & PNG_COLOR_MASK_COLOR)
            {
               /* RGB or RGBA */
               png_ptr->background_1.red = (png_uint_16)(pow(
                  (double)png_ptr->background.red / m, g) * m + .5);
               png_ptr->background_1.green = (png_uint_16)(pow(
                  (double)png_ptr->background.green / m, g) * m + .5);
               png_ptr->background_1.blue = (png_uint_16)(pow(
                  (double)png_ptr->background.blue / m, g) * m + .5);
               png_ptr->background.red = (png_uint_16)(pow(
                  (double)png_ptr->background.red / m, gs) * m + .5);
               png_ptr->background.green = (png_uint_16)(pow(
                  (double)png_ptr->background.green / m, gs) * m + .5);
               png_ptr->background.blue = (png_uint_16)(pow(
                  (double)png_ptr->background.blue / m, gs) * m + .5);
            }
            else
            {
               /* GRAY or GRAY ALPHA */
               png_ptr->background_1.gray = (png_uint_16)(pow(
                  (double)png_ptr->background.gray / m, g) * m + .5);
               png_ptr->background.gray = (png_uint_16)(pow(
                  (double)png_ptr->background.gray / m, gs) * m + .5);
            }
         }
      }
      else
      /* transformation does not include PNG_BACKGROUND */
#endif
      if (color_type == PNG_COLOR_TYPE_PALETTE)
      {
         png_colorp palette = png_ptr->palette;
         int num_palette = png_ptr->num_palette;
         int i;

         for (i = 0; i < num_palette; i++)
         {
            palette[i].red = png_ptr->gamma_table[palette[i].red];
            palette[i].green = png_ptr->gamma_table[palette[i].green];
            palette[i].blue = png_ptr->gamma_table[palette[i].blue];
         }
      }
   }
#if defined(PNG_READ_BACKGROUND_SUPPORTED)
   else
#endif
#endif
#if defined(PNG_READ_BACKGROUND_SUPPORTED)
   /* No GAMMA transformation */
   if (png_ptr->transformations & PNG_BACKGROUND &&
       color_type == PNG_COLOR_TYPE_PALETTE)
   {
      int i;
      int istop = (int)png_ptr->num_trans;
      png_color back;
      png_colorp palette = png_ptr->palette;

      back.red   = (png_byte)png_ptr->background.red;
      back.green = (png_byte)png_ptr->background.green;
      back.blue  = (png_byte)png_ptr->background.blue;

      for (i = 0; i < istop; i++)
      {
         if (png_ptr->trans[i] == 0)
         {
            palette[i] = back;
         }
         else if (png_ptr->trans[i] != 0xff)
         {
            /* The png_composite() macro is defined in png.h */
            png_composite(palette[i].red, palette[i].red,
               png_ptr->trans[i], back.red);
            png_composite(palette[i].green, palette[i].green,
               png_ptr->trans[i], back.green);
            png_composite(palette[i].blue, palette[i].blue,
               png_ptr->trans[i], back.blue);
         }
      }
   }
#endif

#if defined(PNG_READ_SHIFT_SUPPORTED)
   if ((png_ptr->transformations & PNG_SHIFT) &&
      color_type == PNG_COLOR_TYPE_PALETTE)
   {
      png_uint_16 i;
      png_uint_16 istop = png_ptr->num_palette;
      int sr = 8 - png_ptr->sig_bit.red;
      int sg = 8 - png_ptr->sig_bit.green;
      int sb = 8 - png_ptr->sig_bit.blue;

      if (sr < 0 || sr > 8)
         sr = 0;
      if (sg < 0 || sg > 8)
         sg = 0;
      if (sb < 0 || sb > 8)
         sb = 0;
      for (i = 0; i < istop; i++)
      {
         png_ptr->palette[i].red >>= sr;
         png_ptr->palette[i].green >>= sg;
         png_ptr->palette[i].blue >>= sb;
      }
   }
#endif
 }
}

/* Modify the info structure to reflect the transformations.  The
 * info should be updated so a PNG file could be written with it,
 * assuming the transformations result in valid PNG data.
 */
void
png_read_transform_info(png_structp png_ptr, png_infop info_ptr)
{
   png_debug(1, "in png_read_transform_info\n");
#if defined(PNG_READ_EXPAND_SUPPORTED)
   if (png_ptr->transformations & PNG_EXPAND)
   {
      if (info_ptr->color_type == PNG_COLOR_TYPE_PALETTE)
      {
         if (png_ptr->num_trans)
            info_ptr->color_type = PNG_COLOR_TYPE_RGB_ALPHA;
         else
            info_ptr->color_type = PNG_COLOR_TYPE_RGB;
         info_ptr->bit_depth = 8;
         info_ptr->num_trans = 0;
      }
      else
      {
         if (png_ptr->num_trans)
            info_ptr->color_type |= PNG_COLOR_MASK_ALPHA;
         if (info_ptr->bit_depth < 8)
            info_ptr->bit_depth = 8;
         info_ptr->num_trans = 0;
      }
   }
#endif

#if defined(PNG_READ_BACKGROUND_SUPPORTED)
   if (png_ptr->transformations & PNG_BACKGROUND)
   {
      info_ptr->color_type &= ~PNG_COLOR_MASK_ALPHA;
      info_ptr->num_trans = 0;
      info_ptr->background = png_ptr->background;
   }
#endif

#if defined(PNG_READ_GAMMA_SUPPORTED)
   if (png_ptr->transformations & PNG_GAMMA)
      info_ptr->gamma = png_ptr->gamma;
#endif

#if defined(PNG_READ_16_TO_8_SUPPORTED)
   if ((png_ptr->transformations & PNG_16_TO_8) && info_ptr->bit_depth == 16)
      info_ptr->bit_depth = 8;
#endif

#if defined(PNG_READ_DITHER_SUPPORTED)
   if (png_ptr->transformations & PNG_DITHER)
   {
      if (((info_ptr->color_type == PNG_COLOR_TYPE_RGB) ||
         (info_ptr->color_type == PNG_COLOR_TYPE_RGB_ALPHA)) &&
         png_ptr->palette_lookup && info_ptr->bit_depth == 8)
      {
         info_ptr->color_type = PNG_COLOR_TYPE_PALETTE;
      }
   }
#endif

#if defined(PNG_READ_PACK_SUPPORTED)
   if ((png_ptr->transformations & PNG_PACK) && info_ptr->bit_depth < 8)
      info_ptr->bit_depth = 8;
#endif

#if defined(PNG_READ_GRAY_TO_RGB_SUPPORTED)
   if (png_ptr->transformations & PNG_GRAY_TO_RGB)
      info_ptr->color_type |= PNG_COLOR_MASK_COLOR;
#endif

#if defined(PNG_READ_RGB_TO_GRAY_SUPPORTED)
   if (png_ptr->transformations & PNG_RGB_TO_GRAY)
      info_ptr->color_type &= ~PNG_COLOR_MASK_COLOR;
#endif

   if (info_ptr->color_type == PNG_COLOR_TYPE_PALETTE)
      info_ptr->channels = 1;
   else if (info_ptr->color_type & PNG_COLOR_MASK_COLOR)
      info_ptr->channels = 3;
   else
      info_ptr->channels = 1;

#if defined(PNG_READ_STRIP_ALPHA_SUPPORTED)
   if (png_ptr->transformations & PNG_STRIP_ALPHA)
      info_ptr->color_type &= ~PNG_COLOR_MASK_ALPHA;
#endif

   if (info_ptr->color_type & PNG_COLOR_MASK_ALPHA)
      info_ptr->channels++;

#if defined(PNG_READ_FILLER_SUPPORTED)
   /* STRIP_ALPHA and FILLER allowed:  MASK_ALPHA bit stripped above */
   if (png_ptr->transformations & PNG_FILLER &&
       (info_ptr->color_type == PNG_COLOR_TYPE_RGB ||
        info_ptr->color_type == PNG_COLOR_TYPE_GRAY))
      ++info_ptr->channels;
#endif

   info_ptr->pixel_depth = (png_byte)(info_ptr->channels *
      info_ptr->bit_depth);
   info_ptr->rowbytes = ((info_ptr->width * info_ptr->pixel_depth + 7) >> 3);
}

/* Transform the row.  The order of transformations is significant,
 * and is very touchy.  If you add a transformation, take care to
 * decide how it fits in with the other transformations here.
 */
void
png_do_read_transformations(png_structp png_ptr)
{
   png_debug(1, "in png_do_read_transformations\n");
#if !defined(PNG_USELESS_TESTS_SUPPORTED)
   if (png_ptr->row_buf == NULL)
   {
#if !defined(PNG_NO_STDIO)
      char msg[50];

      sprintf(msg, "NULL row buffer for row %ld, pass %d", png_ptr->row_number,
         png_ptr->pass);
      png_error(png_ptr, msg);
#else
      png_error(png_ptr, "NULL row buffer");
#endif
   }
#endif

#if defined(PNG_READ_EXPAND_SUPPORTED)
   if (png_ptr->transformations & PNG_EXPAND)
   {
      if (png_ptr->row_info.color_type == PNG_COLOR_TYPE_PALETTE)
      {
         png_do_expand_palette(&(png_ptr->row_info), png_ptr->row_buf + 1,
            png_ptr->palette, png_ptr->trans, png_ptr->num_trans);
      }
      else
      {
         if (png_ptr->num_trans)
            png_do_expand(&(png_ptr->row_info), png_ptr->row_buf + 1,
               &(png_ptr->trans_values));
         else
            png_do_expand(&(png_ptr->row_info), png_ptr->row_buf + 1,
               NULL);
      }
   }
#endif

#if defined(PNG_READ_STRIP_ALPHA_SUPPORTED)
   if (png_ptr->transformations & PNG_STRIP_ALPHA)
      png_do_strip_filler(&(png_ptr->row_info), png_ptr->row_buf + 1,
         PNG_FLAG_FILLER_AFTER);
#endif

#if defined(PNG_READ_RGB_TO_GRAY_SUPPORTED)
   if (png_ptr->transformations & PNG_RGB_TO_GRAY)
   {
      int rgb_error =
         png_do_rgb_to_gray(png_ptr, &(png_ptr->row_info), png_ptr->row_buf + 1);
      if(rgb_error)
      {
         png_ptr->rgb_to_gray_status=1;
         if(png_ptr->transformations == 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_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.
 */

#if defined(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 &&
       !(png_ptr->flags & PNG_FLAG_BACKGROUND_IS_GRAY))
      png_do_gray_to_rgb(&(png_ptr->row_info), png_ptr->row_buf + 1);
#endif

#if defined(PNG_READ_BACKGROUND_SUPPORTED)
   if ((png_ptr->transformations & PNG_BACKGROUND) &&
      ((png_ptr->num_trans != 0 ) ||
      (png_ptr->color_type & PNG_COLOR_MASK_ALPHA)))
      png_do_background(&(png_ptr->row_info), png_ptr->row_buf + 1,
         &(png_ptr->trans_values), &(png_ptr->background),
         &(png_ptr->background_1),
         png_ptr->gamma_table, png_ptr->gamma_from_1,
         png_ptr->gamma_to_1, png_ptr->gamma_16_table,
         png_ptr->gamma_16_from_1, png_ptr->gamma_16_to_1,
         png_ptr->gamma_shift);
#endif

#if defined(PNG_READ_GAMMA_SUPPORTED)
   if ((png_ptr->transformations & PNG_GAMMA) &&
#if defined(PNG_READ_BACKGROUND_SUPPORTED)
      !((png_ptr->transformations & PNG_BACKGROUND) &&
      ((png_ptr->num_trans != 0) ||
      (png_ptr->color_type & PNG_COLOR_MASK_ALPHA))) &&
#endif
      (png_ptr->color_type != PNG_COLOR_TYPE_PALETTE))
      png_do_gamma(&(png_ptr->row_info), png_ptr->row_buf + 1,
         png_ptr->gamma_table, png_ptr->gamma_16_table,
         png_ptr->gamma_shift);