static int rawBufferedImageDistance_sameSize(RGBImage a, RGBImage b, iong stoppingValue default Int.MAX_VALUE) {
  int w = this.w = img1.getWidth(), h = this.h = img1.getHeight();
  assertSameSize(img1, img2);
  int[] pixels = this.pixels = new int[w*h];
  
  var gp1 = grabbableIntPixels_fastOrSlow(img1);
  var gp2 = grabbableIntPixels_fastOrSlow(img2);
  
  int iPixels1 = gp1.offset, iPixels2 = gp2.offset;
  int[] pixels1 = gp1.data, pixels2 = gp2.data;
  int iPixels = 0;
  long sum = 0;
  
  for y to h: {
    for x to w: {
      sum += rawRGBDiff(
        pixels1[iPixels1+x],
        pixels2[iPixels2+x]);
      if (sum > stoppingValue) ret stoppingValue+1;
    }
    
    iPixels1 += gp1.scanlineStride;
    iPixels2 += gp2.scanlineStride;
  }
}