// result image is as large as the region's bounds

// with black pixels inside and white pixels outside the region

srecord noeq RegionToImage2B(IPixelSet region) {

  settable Rect bounds;

  Image2B image;

  run {

    bounds if null = region.bounds();

    int x1 = bounds.x, y1 = bounds.y, w = bounds.w, h = bounds.h, i = 0;

    byte[] pixels = new[(w*h+7)/8];

    for y to h:

      for x to w: {

        if (!region.contains(x1+x, y1+y))

          pixels[i/8] |= 1 << (i & 7);

        i++;

      }

    image = new Image2B(w, h, pixels);

  }

  Image2B get() {

    if (image == null) run();

    ret image;

  }

}