// A is the user object associated with each mask (aka a "label")
sclass G22MasksHolder<A> {
  record noeq Mask(Image2B image, A label) {
  }

  settable WidthAndHeight maskSize;
  new L<Mask> masks;
  new Set<A> labels;

  // default mask size
  { maskSize(16); }
  
  selfType maskSize(int size) {
    ret maskSize(widthAndHeight(size));
  }
  
  Image2B regionToMaskImage(IImageRegion region) {
    ret toImage2B(scaledIBinaryImage(maskSize, regionToIBinaryImage(region)));
  }
  
  void addRegion(IImageRegion region, A label) {
    masks.add(new Mask(regionToMaskImage(region), label));
    ghost_cache = null;
    certainty_cache = null;
    labels.add(label);
  }
  
  L<Image2B> maskImages() {
    ret map(masks, mask -> mask.image);
  }
  
  BufferedImage masksSquare() {
    ret mergeBufferedImagesAsSquare(allToBufferedImage(maskImages()));
  }
  
  toString {
    ret renderVars(shortClassName(this),
      +maskSize,
      masks := n2(masks),
      +certainty());
  }
  
  simplyCached FloatBWImage ghost() {
    ret preciseAverageOfBinaryImages(maskImages());
  }
  
  simplyCached double certainty() {
    ret preciseCertaintyImage(ghost()).averageBrightness();
  }
}