static BWImage markIntRangesOnTopOfBWImage(BWImage img, L<IntRange> l) {
  int h = 10;
  BWImage bw = new(img.getWidth(), h+img.getHeight());
  copyBWImage(img, 0, 0, bw, 0, h);
  for (IntRange r : unnull(l))
    bwFillRect(bw, r.start, 0, r.end-r.start, h, 1f);
  ret bw;
}