interface IG22MasksHolder<A> {
  replace Mask with IG22Mask<A>.
  
  WidthAndHeight maskSize();
  L<Image2B> maskImages();
  //LPair<Image2B, A> maskImagesWithLabels();
  L<? extends Mask> masks();
  G22GhostImage ghost();
  double certainty();
  default int nMasks() { ret l(masks()); }
  
  default S renderCountAndCertainty() {
    ret main nMasks(nMasks()) + " with c=" + formatDouble3(certainty());
  }
  
  default bool canSplit() { ret nMasks() > 1; }
  
  default L<IG22MasksHolder<A>> subHolders() { null; }
  default void transformSubHolders(IF1<IG22MasksHolder<A>> f) {}
  
  default PStackComputable<Void> findSimilarMasks(G22FindSimilarMasksTask<A> task) {
    ret new FindSimilarMasks_BruteForce<A>(this, task);
  }

  srecord noeq FindSimilarMasks_BruteForce<A>(IG22MasksHolder<A> masksHolder, G22FindSimilarMasksTask<A> task) extends PStackComputableWithStep<Void> {
    Mask maskBeingTested;
    
    toString { ret formatFunctionCall(shortClassName(this), masksHolder, "step=" + step); }
    
    void step(IPStack stack) {
      if (task.ended()) ret with stack.ret();
      if (step == 0) {
        ++step;
        stack.optionsOrReturn(this, map(masksHolder.masks(), mask ->
          self -> self.maskBeingTested = mask));
      } else {
        task.tryMask(maskBeingTested);
        stack.ret();
      }
    }
  }
  
  <B> IG22MasksHolder<B> cloneTreeWithLabelTransform(IF1<A, B> transformLabel);
  
  default L<A> labels() { ret map(masks(), -> .label()); }
  
  default Image2B regionToMaskImage(IImageRegion region) {
    ret region == null ?: g22standardRegionToMaskImage(region, maskSize());
  }
}

Began life as a copy of #1035849