static BufferedImage renderableToImage(Renderable r) {
  if (r == null) null;
  ret renderableToImage(r.preferredSize(), r);
}

static BufferedImage renderableToImage(Pt size, Color backgroundColor default white(), Renderable r) {
  var img = newImage(size.x, size.y, backgroundColor);
  r.renderOn(img, size.x, size.y);
  ret img;
}