static CirclesAndLines calFromCoordinates(Map<S, Pt> coordinates) {
  Rect r = mergeRects(map(f ptToRect, values(coordinates)));
  BufferedImage img = newBufferedImage(20, 20, Color.white);

  new CirclesAndLines cal;
  for (S node : keys(coordinates)) {
    Pt p = coordinates.get(node);
    double x = ((p.x-r.x)/(double) r.w)*0.8+0.1;
    double y = ((p.y-r.y)/(double) r.h)*0.7+0.1;
    cal.circle(img, x, y, node);
  }
  ret cal;
}