svoid fillCircle(Graphics2D g, int x, int y, int r, Color color) {
  g.setColor(color);
  g.fillOval(x-r, y-r, r*2, r*2);
}

svoid fillCircle(BufferedImage img, int x, int y, int r, Color color) {
  fillCircle(imageGraphics(img), x, y, r, color);
}