static float blackHigh_maxBrightness = 0.1f;

static Range blackHigh(RGBImage img, int x, int y) {
  int h = img.h();
  int y1 = y, y2 = y;
  while (y1 > 0 && img.getPixel(x, y1-1).getBrightness() < blackHigh_maxBrightness) --y1;
  while (y2 < h && img.getPixel(x, y2).getBrightness() < blackHigh_maxBrightness) ++y2;
  ret new Range(y1, y2);
}

Began life as a copy of #1006382