static double pixelSetRectangleness_factor = 5;

static double pixelSetRectangleness(PixelSet set) {
  ret (pixelSetRectangleness_dimension(pixelSetBoundsByLine(set))
    + pixelSetRectangleness_dimension(pixelSetBoundsByColumn(set)))/2;
}

static double pixelSetRectangleness_dimension(L<IntRange> l) {
  int[] a = intRangeStarts(l), b = intRangeEnds(l);
  double avgL = doubleAverage(a), avgR = doubleAverage(b);
  double width = avgR-avgL;
  double dev = standardDeviation(b)+standardDeviation(a);
  print("width=" + width + ", dev=" + dev);
  ret max(0, 1-dev*pixelSetRectangleness_factor/width);
}