static RGBImage rgbMarkPoint(RGBImage img, Pt p, Color color, int size) {
  if (img != null &&p != null)
    rgbFillRect(img, p.x-size/2, p.y-size/2, size, size, color);
  ret img;
}

static RGBImage rgbMarkPoint(RGBImage img, Pt p) {
  ret rgbMarkPoint(img, p, Color.red, 3);
}

static RGBImage rgbMarkPoint(RGBImage img, int x, int y) {
  ret rgbMarkPoint(img, new Pt(x, y));
}

static BufferedImage rgbMarkPoint(BufferedImage img, Pt p, Color color, int size default 3) {
  if (img != null &&p != null)
    rgbFillRect(img, p.x-size/2, p.y-size/2, size, size, color);
  ret img;
}