svoid bwDrawRect(BWImage img, int x1, int y1, int w, int h, float color) {
  for y to h: {
    img.setPixel(x1, y1+y, color);
    img.setPixel(x1+w, y1+y, color);
  }
  for x to w: {
    img.setPixel(x1+x, y1, color);
    img.setPixel(x1+x, y1+h, color);
  }
}