static BufferedImage tilesToImage(L<BufferedImage> tiles, int columns) {

  if (empty(tiles)) null;

  int rows = idiv_ceil(l(tiles), columns);

  int tw = first(tiles).getWidth(), th = first(tiles).getHeight();

  int w = tw*columns, h = th*rows;

  BufferedImage img = newBufferedImage(w, h);

  int i = 0, yy = 0;

  for y to rows: {

    int xx = 0;

    for x to columns: {

      if (i >= l(tiles)) break;

      BufferedImage tile = tiles.get(i++);

      copyBufferedImage(tile, img, xx, yy);

      xx += tile.getWidth();

      th = tile.getHeight();

    }

    yy += th;

  }

  ret img;

}