sclass ULetterbox1 implements IIIRecognizer {
 public void run(
    IProbabilisticScheduler scheduler,
    IIntegralImage img,
    IVF1<DoubleRect> valueToAction) {
    var cell   = uCell(img);
    var whole  = cell;
    var middle = cell.slice(1, 1.0/3.0, 1.0/3.0);
    
    // We assume the border is black.
    // If the picture fills the whole screen, it will tend
    // to equal brightness everywhere. Thus whole = middle*3
    // (because it's 3 times as large).
    // If only "middle" is not black, we have whole = middle.
    // Thus the border position can be estimated as:
    
    double borderPos = (2-doubleRatio(whole, middle))*cell.getHeight();
    DoubleRect rect = doubleRectFromPoints(0, borderPos, cell.getWidth(), cell.getHeight()-borderPos);
    
    // No probabilities used.
    
    scheduler.schedule(1.0, () -> valueToAction.get(rect));

    //var antiBorder = cell.slice(1, 1.0/8.0, 1-1/8.0);
    //var border = whole.pixelSum()-antiBorder.pixelSum();
  }
}