sclass BWImageHistogram {
  IBWImage image; // optional
  int[] data; // pixel count for each brightness from 0 to 255
  int nPixels; // sum of pixel count
  
  *(BufferedImage image) {
    this(BWImage(image));
  }
  
  *(BWImage *image) {
    nPixels = area(image);
    data = bwImageHistogramArray(image);
  }
  
  toString { ret "BWImageHistogram of " + nPixels(nPixels)
    + (image == null ? "" : appendBracketed(str_px(image))); }
  
  int[] getArray() { ret data; }
  
  int medianBrightness() {
    int threshold = (nPixels+1)/2, sum = 0;
    for i to 256: {
      sum += data[i];
      if (sum > threshold)
        ret i;
    }
    ret 255;
  }
}