code: private BitMatrix sampleGrid(BitMatrix image,
                                 ResultPoint topLeft,
                                 ResultPoint topRight,
                                 ResultPoint bottomRight,
                                 ResultPoint bottomLeft) throws NotFoundException {
  
      GridSampler sampler = GridSampler.getInstance();
      int dimension = getDimension();
  
      float low = dimension / 2.0f - nbCenterLayers;
      float high = dimension / 2.0f + nbCenterLayers;
  
      return sampler.sampleGrid(image,
                                dimension,
                                dimension,
                                low, low,   // topleft
                                high, low,  // topright
                                high, high, // bottomright
                                low, high,  // bottomleft
                                topLeft.getX(), topLeft.getY(),
                                topRight.getX(), topRight.getY(),
                                bottomRight.getX(), bottomRight.getY(),
                                bottomLeft.getX(), bottomLeft.getY());
    }
docs: Creates a BitMatrix by sampling the provided image.
  topLeft, topRight, bottomRight, and bottomLeft are the centers of the squares on the
  diagonal just outside the bull's eye.