if (pa !== 0) {
        pa = 255 / pa;
        pixels[yi] = ((r_sum * mul_sum) >> shg_sum) * pa;
        pixels[yi + 1] = ((g_sum * mul_sum) >> shg_sum) * pa;
        pixels[yi + 2] = ((b_sum * mul_sum) >> shg_sum) * pa;