static L<Rect> ocr_hsplit(RGBImage img, bool[] split) {

  int w = img.w(), h = img.h();

  int x1 = 0, x = 0;

  new L<Rect> l;

  while (x < w) {

    while (x < w && split[x]) x++;

    if (x > x1) {

      l.add(new Rect(x1, 0, x-x1, h));

      x1 = x;

    }

    while (x < w && !split[x]) x++;

    if (x > x1) {

      l.add(new Rect(x1, 0, x-x1, h));

      x1 = x;

    }

  }

  ret l;

}