pngwutil.c

hl2 source code. Do not use it illegal.

         if (lmhi > PNG_HIMASK)
            lmins = PNG_MAXSUM;
         else
            lmins = (lmhi << PNG_HISHIFT) + lmlo;
      }
#endif

      for (i = 0, rp = row_buf + 1, dp = png_ptr->up_row + 1,
           pp = prev_row + 1; i < row_bytes; i++)
      {
         v = *dp++ = (png_byte)(((int)*rp++ - (int)*pp++) & 0xff);

         sum += (v < 128) ? v : 256 - v;

         if (sum > lmins)  /* We are already worse, don't continue. */
            break;
      }

#if defined(PNG_WRITE_WEIGHTED_FILTER_SUPPORTED)
      if (png_ptr->heuristic_method == PNG_FILTER_HEURISTIC_WEIGHTED)
      {
         int j;
         png_uint_32 sumhi, sumlo;
         sumlo = sum & PNG_LOMASK;
         sumhi = (sum >> PNG_HISHIFT) & PNG_HIMASK;

         for (j = 0; j < num_p_filters; j++)
         {
            if (png_ptr->prev_filters[j] == PNG_FILTER_VALUE_UP)
            {
               sumlo = (sumlo * png_ptr->filter_weights[j]) >>
                  PNG_WEIGHT_SHIFT;
               sumhi = (sumhi * png_ptr->filter_weights[j]) >>
                  PNG_WEIGHT_SHIFT;
            }
         }

         sumlo = (sumlo * png_ptr->filter_costs[PNG_FILTER_VALUE_UP]) >>
            PNG_COST_SHIFT;
         sumhi = (sumhi * png_ptr->filter_costs[PNG_FILTER_VALUE_UP]) >>
            PNG_COST_SHIFT;

         if (sumhi > PNG_HIMASK)
            sum = PNG_MAXSUM;
         else
            sum = (sumhi << PNG_HISHIFT) + sumlo;
      }
#endif

      if (sum < mins)
      {
         mins = sum;
         best_row = png_ptr->up_row;
      }
   }

   /* avg filter */
   if (filter_to_do == PNG_FILTER_AVG)
   {
      png_bytep rp, dp, pp, lp;
      png_uint_32 i;
      for (i = 0, rp = row_buf + 1, dp = png_ptr->avg_row + 1,
           pp = prev_row + 1; i < bpp; i++)
      {
         *dp++ = (png_byte)(((int)*rp++ - ((int)*pp++ / 2)) & 0xff);
      }
      for (lp = row_buf + 1; i < row_bytes; i++)
      {
         *dp++ = (png_byte)(((int)*rp++ - (((int)*pp++ + (int)*lp++) / 2))
                 & 0xff);
      }
      best_row = png_ptr->avg_row;
   }

   else if (filter_to_do & PNG_FILTER_AVG)
   {
      png_bytep rp, dp, pp, lp;
      png_uint_32 sum = 0, lmins = mins;
      png_uint_32 i;
      int v;

#if defined(PNG_WRITE_WEIGHTED_FILTER_SUPPORTED)
      if (png_ptr->heuristic_method == PNG_FILTER_HEURISTIC_WEIGHTED)
      {
         int j;
         png_uint_32 lmhi, lmlo;
         lmlo = lmins & PNG_LOMASK;
         lmhi = (lmins >> PNG_HISHIFT) & PNG_HIMASK;

         for (j = 0; j < num_p_filters; j++)
         {
            if (png_ptr->prev_filters[j] == PNG_FILTER_VALUE_AVG)
            {
               lmlo = (lmlo * png_ptr->inv_filter_weights[j]) >>
                  PNG_WEIGHT_SHIFT;
               lmhi = (lmhi * png_ptr->inv_filter_weights[j]) >>
                  PNG_WEIGHT_SHIFT;
            }
         }

         lmlo = (lmlo * png_ptr->inv_filter_costs[PNG_FILTER_VALUE_AVG]) >>
            PNG_COST_SHIFT;
         lmhi = (lmhi * png_ptr->inv_filter_costs[PNG_FILTER_VALUE_AVG]) >>
            PNG_COST_SHIFT;

         if (lmhi > PNG_HIMASK)
            lmins = PNG_MAXSUM;
         else
            lmins = (lmhi << PNG_HISHIFT) + lmlo;
      }
#endif

      for (i = 0, rp = row_buf + 1, dp = png_ptr->avg_row + 1,
           pp = prev_row + 1; i < bpp; i++)
      {
         v = *dp++ = (png_byte)(((int)*rp++ - ((int)*pp++ / 2)) & 0xff);

         sum += (v < 128) ? v : 256 - v;
      }
      for (lp = row_buf + 1; i < row_bytes; i++)
      {
         v = *dp++ =
          (png_byte)(((int)*rp++ - (((int)*pp++ + (int)*lp++) / 2)) & 0xff);

         sum += (v < 128) ? v : 256 - v;

         if (sum > lmins)  /* We are already worse, don't continue. */
            break;
      }

#if defined(PNG_WRITE_WEIGHTED_FILTER_SUPPORTED)
      if (png_ptr->heuristic_method == PNG_FILTER_HEURISTIC_WEIGHTED)
      {
         int j;
         png_uint_32 sumhi, sumlo;
         sumlo = sum & PNG_LOMASK;
         sumhi = (sum >> PNG_HISHIFT) & PNG_HIMASK;

         for (j = 0; j < num_p_filters; j++)
         {
            if (png_ptr->prev_filters[j] == PNG_FILTER_VALUE_NONE)
            {
               sumlo = (sumlo * png_ptr->filter_weights[j]) >>
                  PNG_WEIGHT_SHIFT;
               sumhi = (sumhi * png_ptr->filter_weights[j]) >>
                  PNG_WEIGHT_SHIFT;
            }
         }

         sumlo = (sumlo * png_ptr->filter_costs[PNG_FILTER_VALUE_AVG]) >>
            PNG_COST_SHIFT;
         sumhi = (sumhi * png_ptr->filter_costs[PNG_FILTER_VALUE_AVG]) >>
            PNG_COST_SHIFT;

         if (sumhi > PNG_HIMASK)
            sum = PNG_MAXSUM;
         else
            sum = (sumhi << PNG_HISHIFT) + sumlo;
      }
#endif

      if (sum < mins)
      {
         mins = sum;
         best_row = png_ptr->avg_row;
      }
   }

   /* Paeth filter */
   if (filter_to_do == PNG_FILTER_PAETH)
   {
      png_bytep rp, dp, pp, cp, lp;
      png_uint_32 i;
      for (i = 0, rp = row_buf + 1, dp = png_ptr->paeth_row + 1,
           pp = prev_row + 1; i < bpp; i++)
      {
         *dp++ = (png_byte)(((int)*rp++ - (int)*pp++) & 0xff);
      }

      for (lp = row_buf + 1, cp = prev_row + 1; i < row_bytes; i++)
      {
         int a, b, c, pa, pb, pc, p;

         b = *pp++;
         c = *cp++;
         a = *lp++;

         p = b - c;
         pc = a - c;

#ifdef PNG_USE_ABS
         pa = abs(p);
         pb = abs(pc);
         pc = abs(p + pc);
#else
         pa = p < 0 ? -p : p;
         pb = pc < 0 ? -pc : pc;
         pc = (p + pc) < 0 ? -(p + pc) : p + pc;
#endif

         p = (pa <= pb && pa <=pc) ? a : (pb <= pc) ? b : c;

         *dp++ = (png_byte)(((int)*rp++ - p) & 0xff);
      }
      best_row = png_ptr->paeth_row;
   }

   else if (filter_to_do & PNG_FILTER_PAETH)
   {
      png_bytep rp, dp, pp, cp, lp;
      png_uint_32 sum = 0, lmins = mins;
      png_uint_32 i;
      int v;

#if defined(PNG_WRITE_WEIGHTED_FILTER_SUPPORTED)
      if (png_ptr->heuristic_method == PNG_FILTER_HEURISTIC_WEIGHTED)
      {
         int j;
         png_uint_32 lmhi, lmlo;
         lmlo = lmins & PNG_LOMASK;
         lmhi = (lmins >> PNG_HISHIFT) & PNG_HIMASK;

         for (j = 0; j < num_p_filters; j++)
         {
            if (png_ptr->prev_filters[j] == PNG_FILTER_VALUE_PAETH)
            {
               lmlo = (lmlo * png_ptr->inv_filter_weights[j]) >>
                  PNG_WEIGHT_SHIFT;
               lmhi = (lmhi * png_ptr->inv_filter_weights[j]) >>
                  PNG_WEIGHT_SHIFT;
            }
         }

         lmlo = (lmlo * png_ptr->inv_filter_costs[PNG_FILTER_VALUE_PAETH]) >>
            PNG_COST_SHIFT;
         lmhi = (lmhi * png_ptr->inv_filter_costs[PNG_FILTER_VALUE_PAETH]) >>
            PNG_COST_SHIFT;

         if (lmhi > PNG_HIMASK)
            lmins = PNG_MAXSUM;
         else
            lmins = (lmhi << PNG_HISHIFT) + lmlo;
      }
#endif

      for (i = 0, rp = row_buf + 1, dp = png_ptr->paeth_row + 1,
           pp = prev_row + 1; i < bpp; i++)
      {
         v = *dp++ = (png_byte)(((int)*rp++ - (int)*pp++) & 0xff);

         sum += (v < 128) ? v : 256 - v;
      }

      for (lp = row_buf + 1, cp = prev_row + 1; i < row_bytes; i++)
      {
         int a, b, c, pa, pb, pc, p;

         b = *pp++;
         c = *cp++;
         a = *lp++;

#ifndef PNG_SLOW_PAETH
         p = b - c;
         pc = a - c;
#ifdef PNG_USE_ABS
         pa = abs(p);
         pb = abs(pc);
         pc = abs(p + pc);
#else
         pa = p < 0 ? -p : p;
         pb = pc < 0 ? -pc : pc;
         pc = (p + pc) < 0 ? -(p + pc) : p + pc;
#endif
         p = (pa <= pb && pa <=pc) ? a : (pb <= pc) ? b : c;
#else /* PNG_SLOW_PAETH */
         p = a + b - c;
         pa = abs(p - a);
         pb = abs(p - b);
         pc = abs(p - c);
         if (pa <= pb && pa <= pc)
            p = a;
         else if (pb <= pc)
            p = b;
         else
            p = c;
#endif /* PNG_SLOW_PAETH */

         v = *dp++ = (png_byte)(((int)*rp++ - p) & 0xff);

         sum += (v < 128) ? v : 256 - v;

         if (sum > lmins)  /* We are already worse, don't continue. */
            break;
      }

#if defined(PNG_WRITE_WEIGHTED_FILTER_SUPPORTED)
      if (png_ptr->heuristic_method == PNG_FILTER_HEURISTIC_WEIGHTED)
      {
         int j;
         png_uint_32 sumhi, sumlo;
         sumlo = sum & PNG_LOMASK;
         sumhi = (sum >> PNG_HISHIFT) & PNG_HIMASK;

         for (j = 0; j < num_p_filters; j++)
         {
            if (png_ptr->prev_filters[j] == PNG_FILTER_VALUE_PAETH)
            {
               sumlo = (sumlo * png_ptr->filter_weights[j]) >>
                  PNG_WEIGHT_SHIFT;
               sumhi = (sumhi * png_ptr->filter_weights[j]) >>
                  PNG_WEIGHT_SHIFT;
            }
         }

         sumlo = (sumlo * png_ptr->filter_costs[PNG_FILTER_VALUE_PAETH]) >>
            PNG_COST_SHIFT;
         sumhi = (sumhi * png_ptr->filter_costs[PNG_FILTER_VALUE_PAETH]) >>
            PNG_COST_SHIFT;

         if (sumhi > PNG_HIMASK)
            sum = PNG_MAXSUM;
         else
            sum = (sumhi << PNG_HISHIFT) + sumlo;
      }
#endif

      if (sum < mins)
      {
         best_row = png_ptr->paeth_row;
      }
   }

   /* Do the actual writing of the filtered row data from the chosen filter. */

   png_write_filtered_row(png_ptr, best_row);

#if defined(PNG_WRITE_WEIGHTED_FILTER_SUPPORTED)
   /* Save the type of filter we picked this time for future calculations */
   if (png_ptr->num_prev_filters > 0)
   {
      int j;
      for (j = 1; j < num_p_filters; j++)
      {
         png_ptr->prev_filters[j] = png_ptr->prev_filters[j - 1];
      }
      png_ptr->prev_filters[j] = best_row[0];
   }
#endif
}


/* Do the actual writing of a previously filtered row. */
void
png_write_filtered_row(png_structp png_ptr, png_bytep filtered_row)
{
   png_debug(1, "in png_write_filtered_row\n");
   png_debug1(2, "filter = %d\n", filtered_row[0]);
   /* set up the zlib input buffer */
   png_ptr->zstream.next_in = filtered_row;
   png_ptr->zstream.avail_in = (uInt)png_ptr->row_info.rowbytes + 1;
   /* repeat until we have compressed all the data */
   do
   {
      int ret; /* return of zlib */

      /* compress the data */
      ret = deflate(&png_ptr->zstream, Z_NO_FLUSH);
      /* check for compression errors */
      if (ret != Z_OK)
      {
         if (png_ptr->zstream.msg != NULL)
            png_error(png_ptr, png_ptr->zstream.msg);
         else
            png_error(png_ptr, "zlib error");
      }

      /* see if it is time to write another IDAT */
      if (!(png_ptr->zstream.avail_out))
      {
         /* write the IDAT and reset the zlib output buffer */
         png_write_IDAT(png_ptr, png_ptr->zbuf, png_ptr->zbuf_size);
         png_ptr->zstream.next_out = png_ptr->zbuf;
         png_ptr->zstream.avail_out = (uInt)png_ptr->zbuf_size;
      }
   /* repeat until all data has been compressed */
   } while (png_ptr->zstream.avail_in);

   /* swap the current and previous rows */
   if (png_ptr->prev_row != NULL)
   {
      png_bytep tptr;

      tptr = png_ptr->prev_row;
      png_ptr->prev_row = png_ptr->row_buf;
      png_ptr->row_buf = tptr;
   }

   /* finish row - updates counters and flushes zlib if last row */
   png_write_finish_row(png_ptr);

#if defined(PNG_WRITE_FLUSH_SUPPORTED)
   png_ptr->flush_rows++;

   if (png_ptr->flush_dist > 0 &&
       png_ptr->flush_rows >= png_ptr->flush_dist)
   {
      png_write_flush(png_ptr);
   }
#endif /* PNG_WRITE_FLUSH_SUPPORTED */
}