docs: private static void thresholdBlock(byte[] luminances,
                                       int xoffset,
                                       int yoffset,
                                       int threshold,
                                       int stride,
                                       BitMatrix matrix) {
      for (int y = 0, offset = yoffset * stride + xoffset; y < BLOCK_SIZE; y++, offset += stride) {
        for (int x = 0; x < BLOCK_SIZE; x++) {
          // Comparison needs to be <= so that black == 0 pixels are black even if the threshold is 0.
          if ((luminances[offset + x] & 0xFF) <= threshold) {
            matrix.set(xoffset + x, yoffset + y);
          }
        }
      }
    }