settable WidthAndHeight maskSize;
  new MultiSet<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)));
  }
  
  L<Image2B> maskImages() {
    ret map(masks(), mask -> mask.image);
  }
  
  BufferedImage masksSquare() {
    ret mergeBufferedImagesAsSquare(allToBufferedImage(maskImages()));
  }
  
  toString {
    ret renderVars(shortClassName(this), +maskSize, masks := n2(masks));
  }
  
  simplyCached FloatBWImage ghost() {
    ret preciseAverageOfBinaryImages(maskImages());
  }
  
  simplyCached double certainty() {
    ret preciseCertaintyImage(ghost()).averageBrightness();
  }
}