static double scoreColorPredicateByRect(F1<Int, Bool> predicate, LPair<RGBImage, Rect> testImages) {
  int score = 0, count = 0;
  for (Pair<RGBImage, Rect> p : testImages) {
    RGBImage img = p.a;
    int w = img.getWidth(), h = img.getHeight();
    //printStructs(+w, +h, r := p.b);
    for y to h:
      for x to w: {
        bool detected = callF(predicate, img.getInt(x, y));
        bool real = rectContains(p.b, x, y);
        score += detected == real ? 1 : 0;
      }
    count += w*h;
  }
  ret doubleRatio(score, count);
}

Began life as a copy of #1022940