static Set<S> thingsOnScreenMap_md5s;

static MultiMap<S, Rect> thingsOnScreenMap() {
  ret thingsOnScreenMap(shootScreenBW());
}
  
static MultiMap<S, Rect> thingsOnScreenMap(BWImage bwScreenShot) {
  SS comments = thingsOnScreenDefinitions();
  L<Rect> segments = autoSegment(bwScreenShot);
  new MultiMap<S, Rect> map;
  new HashSet<S> md5s;
  for (Rect r : segments) {
    RGBImage clip = bwScreenShot.clip(r).toRGB();
    S md5 = rgbMD5(clip);
    md5s.add(md5);
    S text = comments.get(md5);
    if (nempty(text)) map.put(text, r);
  }
  thingsOnScreenMap_md5s = md5s;
  ret map;
}