pngrtran.c

hl2 source code. Do not use it illegal.

                           for (k = 0; k < num_palette; k++)
                           {
                              if (png_ptr->dither_index[k] ==
                                 index_to_palette[j])
                                 png_ptr->dither_index[k] =
                                    index_to_palette[next_j];
                              if ((int)png_ptr->dither_index[k] ==
                                 num_new_palette)
                                 png_ptr->dither_index[k] =
                                    index_to_palette[j];
                           }
                        }

                        index_to_palette[palette_to_index[num_new_palette]] =
                           index_to_palette[j];
                        palette_to_index[index_to_palette[j]] =
                           palette_to_index[num_new_palette];

                        index_to_palette[j] = (png_byte)num_new_palette;
                        palette_to_index[num_new_palette] = (png_byte)j;
                     }
                     if (num_new_palette <= maximum_colors)
                        break;
                  }
                  if (num_new_palette <= maximum_colors)
                     break;
               }
            }

            for (i = 0; i < 769; i++)
            {
               if (hash[i] != NULL)
               {
                  png_dsortp p = hash[i];
                  while (p)
                  {
                     png_dsortp t;

                     t = p->next;
                     png_free(png_ptr, p);
                     p = t;
                  }
               }
               hash[i] = 0;
            }
            max_d += 96;
         }
         png_free(png_ptr, hash);
         png_free(png_ptr, palette_to_index);
         png_free(png_ptr, index_to_palette);
      }
      num_palette = maximum_colors;
   }
   if (png_ptr->palette == NULL)
   {
      png_ptr->palette = palette;
   }
   png_ptr->num_palette = (png_uint_16)num_palette;

   if (full_dither)
   {
      int i;
      png_bytep distance;
      int total_bits = PNG_DITHER_RED_BITS + PNG_DITHER_GREEN_BITS +
         PNG_DITHER_BLUE_BITS;
      int num_red = (1 << PNG_DITHER_RED_BITS);
      int num_green = (1 << PNG_DITHER_GREEN_BITS);
      int num_blue = (1 << PNG_DITHER_BLUE_BITS);
      png_size_t num_entries = ((png_size_t)1 << total_bits);

      png_ptr->palette_lookup = (png_bytep )png_malloc(png_ptr,
         (png_uint_32)(num_entries * sizeof (png_byte)));

      png_memset(png_ptr->palette_lookup, 0, num_entries * sizeof (png_byte));

      distance = (png_bytep)png_malloc(png_ptr, (png_uint_32)(num_entries *
         sizeof(png_byte)));

      png_memset(distance, 0xff, num_entries * sizeof(png_byte));

      for (i = 0; i < num_palette; i++)
      {
         int ir, ig, ib;
         int r = (palette[i].red >> (8 - PNG_DITHER_RED_BITS));
         int g = (palette[i].green >> (8 - PNG_DITHER_GREEN_BITS));
         int b = (palette[i].blue >> (8 - PNG_DITHER_BLUE_BITS));

         for (ir = 0; ir < num_red; ir++)
         {
            int dr = abs(ir - r);
            int index_r = (ir << (PNG_DITHER_BLUE_BITS + PNG_DITHER_GREEN_BITS));

            for (ig = 0; ig < num_green; ig++)
            {
               int dg = abs(ig - g);
               int dt = dr + dg;
               int dm = ((dr > dg) ? dr : dg);
               int index_g = index_r | (ig << PNG_DITHER_BLUE_BITS);

               for (ib = 0; ib < num_blue; ib++)
               {
                  int d_index = index_g | ib;
                  int db = abs(ib - b);
                  int dmax = ((dm > db) ? dm : db);
                  int d = dmax + dt + db;

                  if (d < (int)distance[d_index])
                  {
                     distance[d_index] = (png_byte)d;
                     png_ptr->palette_lookup[d_index] = (png_byte)i;
                  }
               }
            }
         }
      }

      png_free(png_ptr, distance);
   }
}
#endif

#if defined(PNG_READ_GAMMA_SUPPORTED)
/* Transform the image from the file_gamma to the screen_gamma.  We
 * only do transformations on images where the file_gamma and screen_gamma
 * are not close reciprocals, otherwise it slows things down slightly, and
 * also needlessly introduces small errors.
 */
void
png_set_gamma(png_structp png_ptr, double scrn_gamma, double file_gamma)
{
   png_debug(1, "in png_set_gamma\n");
   if (fabs(scrn_gamma * file_gamma - 1.0) > PNG_GAMMA_THRESHOLD)
      png_ptr->transformations |= PNG_GAMMA;
   png_ptr->gamma = (float)file_gamma;
   png_ptr->screen_gamma = (float)scrn_gamma;
}
#endif

#if defined(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
png_set_expand(png_structp png_ptr)
{
   png_debug(1, "in png_set_expand\n");
   png_ptr->transformations |= PNG_EXPAND;
}
#endif

#if defined(PNG_READ_GRAY_TO_RGB_SUPPORTED)
void
png_set_gray_to_rgb(png_structp png_ptr)
{
   png_debug(1, "in png_set_gray_to_rgb\n");
   png_ptr->transformations |= PNG_GRAY_TO_RGB;
}
#endif

#if defined(PNG_READ_RGB_TO_GRAY_SUPPORTED)
/* Convert a RGB image to a grayscale of the same width.  This allows us,
 * for example, to convert a 24 bpp RGB image into an 8 bpp grayscale image.
 */
void
png_set_rgb_to_gray(png_structp png_ptr, int error_action, float red,
  float green)
{
   png_debug(1, "in png_set_rgb_to_gray\n");
   switch(error_action)
   {
      case 1: png_ptr->transformations |= PNG_RGB_TO_GRAY;
              break;
      case 2: png_ptr->transformations |= PNG_RGB_TO_GRAY_WARN;
              break;
      case 3: png_ptr->transformations |= PNG_RGB_TO_GRAY_ERR;
   }
   if (png_ptr->color_type == PNG_COLOR_TYPE_PALETTE)
#if defined(PNG_READ_EXPAND_SUPPORTED)
      png_ptr->transformations |= PNG_EXPAND;
#else
   {
      png_warning(png_ptr, "Cannot do RGB_TO_GRAY without EXPAND_SUPPORTED.");
      png_ptr->transformations &= ~PNG_RGB_TO_GRAY;
   }
#endif
   {
      png_byte red_byte = (png_byte)(red*255.0 + 0.5);
      png_byte green_byte = (png_byte)(green*255.0 + 0.5);
      if(red < 0.0 || green < 0.0)
      {
         red_byte = 54;
         green_byte = 183;
      }
      else if(red_byte + green_byte > 255)
      {
         png_warning(png_ptr, "ignoring out of range rgb_to_gray coefficients");
         red_byte = 54;
         green_byte = 183;
      }
      png_ptr->rgb_to_gray_red_coeff   = red_byte;
      png_ptr->rgb_to_gray_green_coeff = green_byte;
      png_ptr->rgb_to_gray_blue_coeff  = 255 - red_byte - green_byte;
   }
}
#endif

#if defined(PNG_READ_USER_TRANSFORM_SUPPORTED)
void
png_set_read_user_transform_fn(png_structp png_ptr, png_user_transform_ptr
   read_user_transform_fn)
{
   png_debug(1, "in png_set_read_user_transform_fn\n");
   png_ptr->transformations |= PNG_USER_TRANSFORM;
   png_ptr->read_user_transform_fn = read_user_transform_fn;
}
#endif

/* Initialize everything needed for the read.  This includes modifying
 * the palette.
 */
void
png_init_read_transformations(png_structp png_ptr)
{
   png_debug(1, "in png_init_read_transformations\n");
#if defined(PNG_USELESS_TESTS_SUPPORTED)
   if(png_ptr != NULL)
#endif
  {
#if defined(PNG_READ_BACKGROUND_SUPPORTED) || defined(PNG_READ_SHIFT_SUPPORTED) \
 || defined(PNG_READ_GAMMA_SUPPORTED)
   int color_type = png_ptr->color_type;
#endif

#if defined(PNG_READ_EXPAND_SUPPORTED) && defined(PNG_READ_BACKGROUND_SUPPORTED)
   if (png_ptr->transformations & PNG_BACKGROUND_EXPAND)
   {
      if (!(color_type & PNG_COLOR_MASK_COLOR))  /* i.e., GRAY or GRAY_ALPHA */
      {
         /* expand background chunk. */
         switch (png_ptr->bit_depth)
         {
            case 1:
               png_ptr->background.gray *= (png_uint_16)0xff;
               png_ptr->background.red = png_ptr->background.green =
               png_ptr->background.blue = png_ptr->background.gray;
               break;
            case 2:
               png_ptr->background.gray *= (png_uint_16)0x55;
               png_ptr->background.red = png_ptr->background.green =
               png_ptr->background.blue = png_ptr->background.gray;
               break;
            case 4:
               png_ptr->background.gray *= (png_uint_16)0x11;
               png_ptr->background.red = png_ptr->background.green =
               png_ptr->background.blue = png_ptr->background.gray;
               break;
            case 8:
            case 16:
               png_ptr->background.red = png_ptr->background.green =
               png_ptr->background.blue = png_ptr->background.gray;
               break;
         }
      }
      else if (color_type == PNG_COLOR_TYPE_PALETTE)
      {
         png_ptr->background.red   =
            png_ptr->palette[png_ptr->background.index].red;
         png_ptr->background.green =
            png_ptr->palette[png_ptr->background.index].green;
         png_ptr->background.blue  =
            png_ptr->palette[png_ptr->background.index].blue;

#if defined(PNG_READ_INVERT_ALPHA_SUPPORTED)
        if (png_ptr->transformations & PNG_INVERT_ALPHA)
        {
#if defined(PNG_READ_EXPAND_SUPPORTED)
           if (!(png_ptr->transformations & PNG_EXPAND))
#endif
           {
           /* invert the alpha channel (in tRNS) unless the pixels are
              going to be expanded, in which case leave it for later */
              int i,istop;
              istop=(int)png_ptr->num_trans;
              for (i=0; i<istop; i++)
                 png_ptr->trans[i] = 255 - png_ptr->trans[i];
           }
        }
#endif

      }
   }
#endif

#if defined(PNG_READ_BACKGROUND_SUPPORTED)
   png_ptr->background_1 = png_ptr->background;
#endif
#if defined(PNG_READ_GAMMA_SUPPORTED)
   if (png_ptr->transformations & (PNG_GAMMA | PNG_RGB_TO_GRAY))
   {
      png_build_gamma_table(png_ptr);
#if defined(PNG_READ_BACKGROUND_SUPPORTED)
      if (png_ptr->transformations & PNG_BACKGROUND)
      {
         if (color_type == PNG_COLOR_TYPE_PALETTE)
         {
            png_color back, back_1;
            png_colorp palette = png_ptr->palette;
            int num_palette = png_ptr->num_palette;
            int i;

            if (png_ptr->background_gamma_type == PNG_BACKGROUND_GAMMA_FILE)
            {
               back.red = png_ptr->gamma_table[png_ptr->background.red];
               back.green = png_ptr->gamma_table[png_ptr->background.green];
               back.blue = png_ptr->gamma_table[png_ptr->background.blue];

               back_1.red = png_ptr->gamma_to_1[png_ptr->background.red];
               back_1.green = png_ptr->gamma_to_1[png_ptr->background.green];
               back_1.blue = png_ptr->gamma_to_1[png_ptr->background.blue];
            }
            else
            {
               double g, gs;

               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;
                  default:
                     g = 1.0;    /* back_1 */
                     gs = 1.0;   /* back */
               }

               if ( fabs(gs - 1.0) < PNG_GAMMA_THRESHOLD)
               {
                  back.red   = (png_byte)png_ptr->background.red;
                  back.green = (png_byte)png_ptr->background.green;
                  back.blue  = (png_byte)png_ptr->background.blue;
               }
               else
               {
                  back.red = (png_byte)(pow(
                     (double)png_ptr->background.red/255, gs) * 255.0 + .5);
                  back.green = (png_byte)(pow(
                     (double)png_ptr->background.green/255, gs) * 255.0 + .5);
                  back.blue = (png_byte)(pow(
                     (double)png_ptr->background.blue/255, gs) * 255.0 + .5);
               }

               back_1.red = (png_byte)(pow(
                  (double)png_ptr->background.red/255, g) * 255.0 + .5);
               back_1.green = (png_byte)(pow(
                  (double)png_ptr->background.green/255, g) * 255.0 + .5);
               back_1.blue = (png_byte)(pow(
                  (double)png_ptr->background.blue/255, g) * 255.0 + .5);
            }

            for (i = 0; i < num_palette; i++)
            {
               if (i < (int)png_ptr->num_trans && png_ptr->trans[i] != 0xff)
               {
                  if (png_ptr->trans[i] == 0)
                  {
                     palette[i] = back;
                  }
                  else /* if (png_ptr->trans[i] != 0xff) */
                  {
                     png_byte v, w;

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