static void fillTriangle(BufferedImage image, int x1, int y1, int x2, int y2, int x3, int y3, Color color) {
  Graphics2D g = imageGraphics(image);
  g.setColor(color);
  g.fillPolygon(intArray(x1, x2, x3), intArray(y1, y2, y3), 3);
  g.dispose();
}

// draw on currentImage()
static void fillTriangle(int x1, int y1, int x2, int y2, int x3, int y3, Color color) {
  fillTriangle(currentImage(), x1, y1, x2, y2, x3, y3, color);
}

static void fillTriangle(Pt a, Pt b, Pt c, Color color) {
  fillTriangle(a.x, a.y, b.x, b.y, c.x, c.y, color);
}