svoid overlaySelectionsOnImageSurface(final ImageSurface is, final L<Rect> rects) {
  if (is == null) ret;
  is.overlay = voidfunc(Graphics2D g) {
    for (Rect r : rects)
      is.drawSelectionRect(g, r.getRectangle(), Color.blue, Color.white);
  };
  is.repaint();
}