onlyCr rgb = Ycbcr.fromYcbcr (128, 0.0, cr)
  where (y, cb, cr) = Ycbcr.toYcbcr rgb
onlyCr rgb = Ycbcr.fromYcbcr (128, 0.0, cr)
  where (y, cb, cr) = Ycbcr.toYcbcr rgb
onlyCr rgb = Ycbcr.fromYcbcr (128, 0.0, cr)
  where (y, cb, cr) = Ycbcr.toYcbcr rgb