static Image2B image2BFromFunction(int w, int h default w, IIntIntPred f) {
  Image2B img = new(w, h);
  for y to h:
    for x to w:
      img.setPixel(x, y, f.get(x, y));
  ret img;
}

static Image2B image2BFromFunction(int w, int h default w, IF0_Bool f) {
  ret image2BFromFunction(w, h, (x, y) -> f!);
}

Began life as a copy of #1026933