static RGBImage greenWhiteMarkedImage(RGBImage image, bool[] mark) {
  int w = image.getWidth(), h = image.getHeight();
  RGBImage i = new RGBImage(w, h);
  for y to h: for x to w:
    i.setPixel(x, y, get(mark, y*w+x)
      ? greenWhiteMarkedImage_color(x, y)
      : image.getInt(x, y));
  ret i;
}

static int greenWhiteMarkedImage_color(int x, int y) {
  ret odd(x+y) ? 0xFFFFFF : 0x00FF00;
}