yy, cb, cr := color.RGBToYCbCr(pix[0], pix[1], pix[2])
			yBlock[8*j+i] = int32(yy)
			cbBlock[8*j+i] = int32(cb)
			crBlock[8*j+i] = int32(cr)
		}
	}
}

// yCbCrToYCbCr is a specialized version of toYCbCr for image.YCbCr images.
func yCbCrToYCbCr(m *image.YCbCr, p image.Point, yBlock, cbBlock, crBlock *block) {
	b := m.Bounds()
	xmax := b.Max.X - 1
	ymax := b.Max.Y - 1
	for j := 0; j < 8; j++ {
		sy := p.Y + j