static BufferedImage tilesToImage_twoLevelList(LL<BufferedImage> tiles) {

  if (empty(tiles)) null;

  int columns = maxLength(tiles);

  int rows = l(tiles);

  int w = intSum(mapMethod getWidth(first(tiles)));

  int h = intSum(mapMethod getWidth(map first(tiles)));

  BufferedImage img = newBufferedImage(w, h);

  int yy = 0;

  for y to rows: {

    int xx = 0, th = 0;

    for x to columns: {

      BufferedImage tile = get(tiles.get(y), x);

      if (tile != null) {

        copyBufferedImage(tile, img, xx, yy);

        xx += tile.getWidth();

        th = tile.getHeight();

      }

    }

    yy += th;

  }

  ret img;

}