func (p *YCbCr) RGBA64At(x, y int) color.RGBA64 {
	r, g, b, a := p.YCbCrAt(x, y).RGBA()
	return color.RGBA64{uint16(r), uint16(g), uint16(b), uint16(a)}
}

func (p *YCbCr) YCbCrAt(x, y int) color.YCbCr {
	if !(Point{x, y}.In(p.Rect)) {
		return color.YCbCr{}
	}
	yi := p.YOffset(x, y)
	ci := p.COffset(x, y)
	return color.YCbCr{
		p.Y[yi],
		p.Cb[ci],
		p.Cr[ci],
	}
}

}

// YCbCrModel is the [Model] for Y'CbCr colors.
var YCbCrModel Model = ModelFunc(yCbCrModel)

func yCbCrModel(c Color) Color {
	if _, ok := c.(YCbCr); ok {
		return c
	}
	r, g, b, _ := c.RGBA()
	y, u, v := RGBToYCbCr(uint8(r>>8), uint8(g>>8), uint8(b>>8))
	return YCbCr{y, u, v}
}

// NYCbCrA represents a non-alpha-premultiplied Y'CbCr-with-alpha color, having

	default:
		rgba, _ := m.(*image.RGBA)
		ycbcr, _ := m.(*image.YCbCr)
		for y := bounds.Min.Y; y < bounds.Max.Y; y += 16 {
			for x := bounds.Min.X; x < bounds.Max.X; x += 16 {
				for i := 0; i < 4; i++ {
					xOff := (i & 1) * 8
					yOff := (i & 2) * 4
					p := image.Pt(x+xOff, y+yOff)
					if rgba != nil {
						rgbaToYCbCr(rgba, p, &b, &cb[i], &cr[i])
					} else if ycbcr != nil {

	// or CMYK)" as per
	// https://www.sno.phy.queensu.ca/~phil/exiftool/TagNames/JPEG.html#Adobe
	// we assume that it is YCbCrK. This matches libjpeg's jdapimin.c.
	if d.adobeTransform != adobeTransformUnknown {
		// Convert the YCbCr part of the YCbCrK to RGB, invert the RGB to get
		// CMY, and patch in the original K. The RGB to CMY inversion cancels

		return c
	}
	r, g, b, _ := c.RGBA()

	// These coefficients (the fractions 0.299, 0.587 and 0.114) are the same
	// as those given by the JFIF specification and used by func RGBToYCbCr in
	// ycbcr.go.
	//
	// Note that 19595 + 38470 + 7471 equals 65536.
	//
	// The 24 is 16 + 8. The 16 is the same as used in RGBToYCbCr. The 8 is
	// because the return value is 8 bit color, not 16 bit color.

		if m0.Bounds() != image.Rect(0, 0, 150, 103) {
			t.Errorf("%s: bad bounds: %v", tc, m0.Bounds())
			continue
		}

		switch m0 := m0.(type) {
		case *image.YCbCr:
			m1 := m1.(*image.YCbCr)
			if err := check(m0.Bounds(), m0.Y, m1.Y, m0.YStride, m1.YStride); err != nil {
				t.Errorf("%s (Y): %v", tc, err)
				continue
			}

		subsampleRatio = image.YCbCrSubsampleRatio410
	default:
		panic("unreachable")
	}
	m := image.NewYCbCr(image.Rect(0, 0, 8*h0*mxx, 8*v0*myy), subsampleRatio)
	d.img3 = m.SubImage(image.Rect(0, 0, d.width, d.height)).(*image.YCbCr)

	if d.nComp == 4 {
		h3, v3 := d.comp[3].h, d.comp[3].v
		d.blackPix = make([]byte, 8*h3*mxx*8*v3*myy)
		d.blackStride = 8 * h3 * mxx
	}
}

// Specified in section B.2.3.

					}
					return
				case *image.RGBA:
					drawCopyOver(dst0, r, src0, sp)
					return
				case *image.NRGBA:
					drawNRGBAOver(dst0, r, src0, sp)
					return
				case *image.YCbCr:
					// An image.YCbCr is always fully opaque, and so if the
					// mask is nil (i.e. fully opaque) then the op is
					// effectively always Src. Similarly for image.Gray and
					// image.CMYK.

		{"(*Uniform).RGBA64At", Method, 17},
		{"(*YCbCr).At", Method, 0},
		{"(*YCbCr).Bounds", Method, 0},
		{"(*YCbCr).COffset", Method, 0},
		{"(*YCbCr).ColorModel", Method, 0},
		{"(*YCbCr).Opaque", Method, 0},
		{"(*YCbCr).RGBA64At", Method, 17},
		{"(*YCbCr).SubImage", Method, 0},
		{"(*YCbCr).YCbCrAt", Method, 4},
		{"(*YCbCr).YOffset", Method, 0},
		{"(Point).Add", Method, 0},