type YCbCrSubsampleRatio int

const (
	YCbCrSubsampleRatio444 YCbCrSubsampleRatio = iota
	YCbCrSubsampleRatio422
	YCbCrSubsampleRatio420
	YCbCrSubsampleRatio440
	YCbCrSubsampleRatio411
	YCbCrSubsampleRatio410
)

func (s YCbCrSubsampleRatio) String() string {
	switch s {
	case YCbCrSubsampleRatio444:
		return "YCbCrSubsampleRatio444"
	case YCbCrSubsampleRatio422:
		return "YCbCrSubsampleRatio422"

		}
		src = &image.YCbCr{
			Y:              yy,
			Cb:             cb,
			Cr:             cr,
			YStride:        srcw,
			CStride:        srcw,
			SubsampleRatio: image.YCbCrSubsampleRatio444,
			Rect:           image.Rect(0, 0, srcw, srch),
		}
	default:
		b.Fatal("unknown source color model", scm)
	}

	var mask image.Image
	switch mcm {
	case nil:
		// No-op.

func TestEncodeYCbCr(t *testing.T) {
	bo := image.Rect(0, 0, 640, 480)
	imgRGBA := image.NewRGBA(bo)
	// Must use 444 subsampling to avoid lossy RGBA to YCbCr conversion.
	imgYCbCr := image.NewYCbCr(bo, image.YCbCrSubsampleRatio444)
	rnd := rand.New(rand.NewSource(123))
	// Create identical rgba and ycbcr images.
	for y := bo.Min.Y; y < bo.Max.Y; y++ {
		for x := bo.Min.X; x < bo.Max.X; x++ {
			col := color.RGBA{

	h0 := d.comp[0].h
	v0 := d.comp[0].v
	hRatio := h0 / d.comp[1].h
	vRatio := v0 / d.comp[1].v
	var subsampleRatio image.YCbCrSubsampleRatio
	switch hRatio<<4 | vRatio {
	case 0x11:
		subsampleRatio = image.YCbCrSubsampleRatio444
	case 0x12:
		subsampleRatio = image.YCbCrSubsampleRatio440
	case 0x21:
		subsampleRatio = image.YCbCrSubsampleRatio422
	case 0x22:
		subsampleRatio = image.YCbCrSubsampleRatio420
	case 0x41:

	m := &image.YCbCr{
		Y:              make([]byte, 16*16),
		Cb:             make([]byte, 16*16),
		Cr:             make([]byte, 16*16),
		YStride:        16,
		CStride:        16,
		SubsampleRatio: image.YCbCrSubsampleRatio444,
		Rect:           image.Rect(0, 0, 16, 16),
	}
	for y := 0; y < 16; y++ {
		for x := 0; x < 16; x++ {
			m.Cr[y*m.CStride+x] = uint8(y * 0x11)
		}
	}
	return m
}

		{"YCbCrSubsampleRatio410", Const, 5},
		{"YCbCrSubsampleRatio411", Const, 5},
		{"YCbCrSubsampleRatio420", Const, 0},
		{"YCbCrSubsampleRatio422", Const, 0},
		{"YCbCrSubsampleRatio440", Const, 1},
		{"YCbCrSubsampleRatio444", Const, 0},
		{"ZP", Var, 0},
		{"ZR", Var, 0},
	},
	"image/color": {
		{"(Alpha).RGBA", Method, 0},
		{"(Alpha16).RGBA", Method, 0},
		{"(CMYK).RGBA", Method, 5},