sclass BWImageCategorizer {
  new L<BWImage> images;
  float allowedDistance = 0.1f; // allowed difference within category
  
  *() {}
  *(float *allowedDistance) {}
  
  int locateImage(BWImage img) {
    for i over images:
      if (bwDistance(images.get(i), img, allowedDistance) <= allowedDistance)
        ret i;
    ret -1;
  }
  
  int addImage(RGBImage img) { ret addImage(new BWImage(img)); }
  
  int addImage(BWImage img) {
    int i = locateImage(img);
    if (i >= 0) ret i;
    images.add(img);
    ret l(images)-1;
  }
  
  int numCategories() { ret l(images); }
  void clear() { images.clear(); }
  
  L<RGBImage> rgbImages() { ret bwImagesToRGB(images); }
  
  // find best fit regardless of distance
  // returns Pair<index, confidence>
  Pair<Int, Float> locateLax(BWImage img) {
    new Lowest<Int> l;
    for i over images:
      l.put(i, bwDistance(images.get(i), img));
    ret pair(or(l.get(), -1), 1f-l.floatScoreOr(1));
  }
}

Began life as a copy of #1006761