bench(b, color.RGBAModel, color.NRGBAModel, nil, Over)
}

func BenchmarkNRGBASrc(b *testing.B) {
	bench(b, color.RGBAModel, color.NRGBAModel, nil, Src)
}

func BenchmarkYCbCr(b *testing.B) {
	bench(b, color.RGBAModel, color.YCbCrModel, nil, Over)
}

func BenchmarkGray(b *testing.B) {
	bench(b, color.RGBAModel, color.GrayModel, nil, Over)
}

func BenchmarkCMYK(b *testing.B) {

	NRGBAModel   Model = ModelFunc(nrgbaModel)
	NRGBA64Model Model = ModelFunc(nrgba64Model)
	AlphaModel   Model = ModelFunc(alphaModel)
	Alpha16Model Model = ModelFunc(alpha16Model)
	GrayModel    Model = ModelFunc(grayModel)
	Gray16Model  Model = ModelFunc(gray16Model)
)

func rgbaModel(c Color) Color {
	if _, ok := c.(RGBA); ok {
		return c
	}
	r, g, b, a := c.RGBA()

// Unlike slowerRGBA, it does not implement the draw.RGBA64Image interface.
type slowestRGBA struct {
	Pix    []uint8
	Stride int
	Rect   image.Rectangle
}

func (p *slowestRGBA) ColorModel() color.Model { return color.RGBAModel }

func (p *slowestRGBA) Bounds() image.Rectangle { return p.Rect }

func (p *slowestRGBA) At(x, y int) color.Color {
	return p.RGBA64At(x, y)
}

func (p *slowestRGBA) RGBA64At(x, y int) color.RGBA64 {

func sng(w io.WriteCloser, filename string, png image.Image) {
	defer w.Close()
	bounds := png.Bounds()
	cm := png.ColorModel()
	var bitdepth int
	switch cm {
	case color.RGBAModel, color.NRGBAModel, color.AlphaModel, color.GrayModel:
		bitdepth = 8
	default:
		bitdepth = 16
	}
	cpm, _ := cm.(color.Palette)
	var paletted *image.Paletted
	if cpm != nil {
		switch {
		case len(cpm) <= 2:

			e.cb = cbP4
		} else {
			e.cb = cbP8
		}
	} else {
		switch m.ColorModel() {
		case color.GrayModel:
			e.cb = cbG8
		case color.Gray16Model:
			e.cb = cbG16
		case color.RGBAModel, color.NRGBAModel, color.AlphaModel:
			if opaque(m) {
				e.cb = cbTC8
			} else {
				e.cb = cbTCA8
			}
		default:
			if opaque(m) {
				e.cb = cbTC16
			} else {
				e.cb = cbTCA16
			}
		}

	Pix []uint8
	// Stride is the Pix stride (in bytes) between vertically adjacent pixels.
	Stride int
	// Rect is the image's bounds.
	Rect Rectangle
}

func (p *RGBA) ColorModel() color.Model { return color.RGBAModel }

func (p *RGBA) Bounds() Rectangle { return p.Rect }

func (p *RGBA) At(x, y int) color.Color {
	return p.RGBAAt(x, y)
}

func (p *RGBA) RGBA64At(x, y int) color.RGBA64 {

	}

	var cm color.Model
	switch d.cb {
	case cbG1, cbG2, cbG4, cbG8:
		cm = color.GrayModel
	case cbGA8:
		cm = color.NRGBAModel
	case cbTC8:
		cm = color.RGBAModel
	case cbP1, cbP2, cbP4, cbP8:
		cm = d.palette
	case cbTCA8:
		cm = color.NRGBAModel
	case cbG16:
		cm = color.Gray16Model
	case cbGA16:
		cm = color.NRGBA64Model
	case cbTC16:
		cm = color.RGBA64Model

	case 1:
		return image.Config{
			ColorModel: color.GrayModel,
			Width:      d.width,
			Height:     d.height,
		}, nil
	case 3:
		cm := color.YCbCrModel
		if d.isRGB() {
			cm = color.RGBAModel
		}
		return image.Config{
			ColorModel: cm,
			Width:      d.width,
			Height:     d.height,
		}, nil
	case 4:
		return image.Config{
			ColorModel: color.CMYKModel,
			Width:      d.width,

		{"RGBA.R", Field, 0},
		{"RGBA64", Type, 0},
		{"RGBA64.A", Field, 0},
		{"RGBA64.B", Field, 0},
		{"RGBA64.G", Field, 0},
		{"RGBA64.R", Field, 0},
		{"RGBA64Model", Var, 0},
		{"RGBAModel", Var, 0},
		{"RGBToCMYK", Func, 5},
		{"RGBToYCbCr", Func, 0},
		{"Transparent", Var, 0},
		{"White", Var, 0},
		{"YCbCr", Type, 0},
		{"YCbCr.Cb", Field, 0},
		{"YCbCr.Cr", Field, 0},

pkg image/color, var Gray16Model Model
pkg image/color, var GrayModel Model
pkg image/color, var NRGBA64Model Model
pkg image/color, var NRGBAModel Model
pkg image/color, var Opaque Alpha16
pkg image/color, var RGBA64Model Model
pkg image/color, var RGBAModel Model
pkg image/color, var Transparent Alpha16
pkg image/color, var White Gray16
pkg image/color, var YCbCrModel Model
pkg image/draw, const Over Op