code: private static boolean checkPixel(MapTile map, ImageBuffer tileRef, int progressTileX, int progressTileY)
      {
          final int x = progressTileX * map.getTileWidth();
          final int y = progressTileY * map.getTileHeight();
          final int pixel = tileRef.getRgb(x, y);
  
          // Skip blank tile of image map
          if (TilesExtractor.IGNORED_COLOR_VALUE != pixel)
          {
              // Search if tile is on sheet and get it
              final Tile tile = searchForTile(map, tileRef, progressTileX, progressTileY);
              if (tile == null)
              {
                  return false;
              }
              map.setTile(tile);
          }
          return true;
      }
docs: Check the pixel by searching tile on sheet.
  
  @param map The destination map reference.
  @param tileRef The tile sheet.
  @param progressTileX The progress on horizontal tiles.
  @param progressTileY The progress on vertical tiles.
  @return <code>true</code> if tile found, <code>false</code> else.