static SkIRect rand_rect(SkMWCRandom& rand, int n) {
    int x = rand.nextS() % n;
    int y = rand.nextS() % n;
    int w = rand.nextU() % n;
    int h = rand.nextU() % n;
    return SkIRect::MakeXYWH(x, y, w, h);
}
static void rand_array(SkMWCRandom& rand, int array[], int n) {
    for (int j = 0; j < n; j++) {
        array[j] = rand.nextS() & 0xFF;
    }
}