code: func newYCC(r image.Rectangle, s image.YCbCrSubsampleRatio) *ycc {
  	w, h := r.Dx(), r.Dy()
  	buf := make([]uint8, 3*w*h)
  	return &ycc{Pix: buf, Stride: 3 * w, Rect: r, SubsampleRatio: s}
  }
docs: // newYCC returns a new ycc with the given bounds and subsample ratio.