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"

		NewAlpha(r),
		NewAlpha16(r),
		NewCMYK(r),
		NewGray(r),
		NewGray16(r),
		NewNRGBA(r),
		NewNRGBA64(r),
		NewNYCbCrA(r, YCbCrSubsampleRatio444),
		NewPaletted(r, palette.Plan9),
		NewRGBA(r),
		NewRGBA64(r),
		NewUniform(color.RGBA64{}),
		NewYCbCr(r, YCbCrSubsampleRatio444),
		r,
	}
	for _, tc := range testCases {
		switch tc := tc.(type) {

		Rect(7, 8, 8, 9),
		Rect(8, 7, 9, 8),
		Rect(8, 8, 9, 9),
		Rect(7, 7, 17, 17),
		Rect(8, 8, 17, 17),
		Rect(9, 9, 17, 17),
		Rect(10, 10, 17, 17),
	}
	subsampleRatios := []YCbCrSubsampleRatio{
		YCbCrSubsampleRatio444,
		YCbCrSubsampleRatio422,
		YCbCrSubsampleRatio420,
		YCbCrSubsampleRatio440,
		YCbCrSubsampleRatio411,
		YCbCrSubsampleRatio410,
	}
	deltas := []Point{
		Pt(0, 0),
		Pt(1000, 1001),

		}
		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{

	x0 := (r.Min.X - dst.Rect.Min.X) * 4
	x1 := (r.Max.X - dst.Rect.Min.X) * 4
	y0 := r.Min.Y - dst.Rect.Min.Y
	y1 := r.Max.Y - dst.Rect.Min.Y
	switch src.SubsampleRatio {

	case image.YCbCrSubsampleRatio444:
		for y, sy := y0, sp.Y; y != y1; y, sy = y+1, sy+1 {
			dpix := dst.Pix[y*dst.Stride:]
			yi := (sy-src.Rect.Min.Y)*src.YStride + (sp.X - src.Rect.Min.X)

	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},

pkg html/template, type Template struct
pkg html/template, type URL string
pkg image, const YCbCrSubsampleRatio420 YCbCrSubsampleRatio
pkg image, const YCbCrSubsampleRatio422 YCbCrSubsampleRatio
pkg image, const YCbCrSubsampleRatio444 YCbCrSubsampleRatio
pkg image, func Decode(io.Reader) (Image, string, error)
pkg image, func DecodeConfig(io.Reader) (Config, string, error)
pkg image, func NewAlpha(Rectangle) *Alpha