static ItIt<ParameterizedSegmenter> chessOCR_adaptSegmenterToMainImageColors(BufferedImage img, ParameterizedSegmenter baseSegmenter, O... _) {
  optPar int maxColors = 10; // try 10 top colors
  MultiSet<S> histogram = histogram332(img);
  ret takeFirstI(maxColors, mapI(histogram.highestFirst(),
    color -> {
      ParameterizedSegmenter seg = shallowNonTransientClone(baseSegmenter);
      seg.distanceFromColor(color332toRGB(color));
      ret seg;
    }));
}