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sclass OCRCompass {
  IBWIntegralImage image;
  Pt center; // point we're looking at
  double radius = 16; // radius of circle
  int sensorFootprint = 4; // size of each "pixel" (rectangle) to grab
  int steps = 12; // how many segments of circle (=steps/2 line orientations). should be even
  int blur; // blur width
  double[] values; // brightnesses at each point (low=foreground)
  
  L<Rect> sensors() {
    ret squaresAroundCircle(center, steps, radius, sensorFootprint);
  }
  
  void compute {
    values = mapToDoubleArray(sensors(),
      r -> image.getPixelAverage(r));
  }
  
  void ensureComputed {
    if (values == null) compute();
  }
  
  double mostLikelyAngle() {
    ensureComputed();
    indexOfMaxEntryInDoubleArray(values);
    ret twoPi()/steps;
  }
}