Source: image.go in package image

Package image implements a basic 2-D image library. The fundamental interface is called Image. An Image contains colors, which are described in the image/color package. Values of the Image interface are created either by calling functions such as NewRGBA and NewPaletted, or by calling Decode on an io.Reader containing image data in a format such as GIF, JPEG or PNG. Decoding any particular image format requires the prior registration of a decoder function. Registration is typically automatic as a side effect of initializing that format's package so that, to decode a PNG image, it suffices to have import _ "image/png" in a program's main package. The _ means to import a package purely for its initialization side effects. See "The Go image package" for more details: https://golang.org/doc/articles/image_package.html

package image

import (
	"image/color"
)

Config holds an image's color model and dimensions.

type Config struct {
	ColorModel    color.Model
	Width, Height int
}

Image is a finite rectangular grid of color.Color values taken from a color model.

ColorModel returns the Image's color model.

Bounds returns the domain for which At can return non-zero color. The bounds do not necessarily contain the point (0, 0).

At returns the color of the pixel at (x, y). At(Bounds().Min.X, Bounds().Min.Y) returns the upper-left pixel of the grid. At(Bounds().Max.X-1, Bounds().Max.Y-1) returns the lower-right one.

	At(x, y int) color.Color
}

PalettedImage is an image whose colors may come from a limited palette. If m is a PalettedImage and m.ColorModel() returns a color.Palette p, then m.At(x, y) should be equivalent to p[m.ColorIndexAt(x, y)]. If m's color model is not a color.Palette, then ColorIndexAt's behavior is undefined.

ColorIndexAt returns the palette index of the pixel at (x, y).

	ColorIndexAt(x, y int) uint8
	Image
}

pixelBufferLength returns the length of the []uint8 typed Pix slice field for the NewXxx functions. Conceptually, this is just (bpp * width * height), but this function panics if at least one of those is negative or if the computation would overflow the int type. This panics instead of returning an error because of backwards compatibility. The NewXxx functions do not return an error.

func pixelBufferLength(bytesPerPixel int, r Rectangle, imageTypeName string) int {
	totalLength := mul3NonNeg(bytesPerPixel, r.Dx(), r.Dy())
	if totalLength < 0 {
		panic("image: New" + imageTypeName + " Rectangle has huge or negative dimensions")
	}
	return totalLength
}

RGBA is an in-memory image whose At method returns color.RGBA values.

Pix holds the image's pixels, in R, G, B, A order. The pixel at (x, y) starts at Pix[(y-Rect.Min.Y)*Stride + (x-Rect.Min.X)*4].

Stride is the Pix stride (in bytes) between vertically adjacent pixels.

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) RGBAAt(x, y int) color.RGBA {
	if !(Point{x, y}.In(p.Rect)) {
		return color.RGBA{}
	}
	i := p.PixOffset(x, y)
	s := p.Pix[i : i+4 : i+4] // Small cap improves performance, see https://golang.org/issue/27857
	return color.RGBA{s[0], s[1], s[2], s[3]}
}

PixOffset returns the index of the first element of Pix that corresponds to the pixel at (x, y).

func (p *RGBA) PixOffset(x, y int) int {
	return (y-p.Rect.Min.Y)*p.Stride + (x-p.Rect.Min.X)*4
}

func (p *RGBA) Set(x, y int, c color.Color) {
	if !(Point{x, y}.In(p.Rect)) {
		return
	}
	i := p.PixOffset(x, y)
	c1 := color.RGBAModel.Convert(c).(color.RGBA)
	s := p.Pix[i : i+4 : i+4] // Small cap improves performance, see https://golang.org/issue/27857
	s[0] = c1.R
	s[1] = c1.G
	s[2] = c1.B
	s[3] = c1.A
}

func (p *RGBA) SetRGBA(x, y int, c color.RGBA) {
	if !(Point{x, y}.In(p.Rect)) {
		return
	}
	i := p.PixOffset(x, y)
	s := p.Pix[i : i+4 : i+4] // Small cap improves performance, see https://golang.org/issue/27857
	s[0] = c.R
	s[1] = c.G
	s[2] = c.B
	s[3] = c.A
}

SubImage returns an image representing the portion of the image p visible through r. The returned value shares pixels with the original image.

func (p *RGBA) SubImage(r Rectangle) Image {

If r1 and r2 are Rectangles, r1.Intersect(r2) is not guaranteed to be inside either r1 or r2 if the intersection is empty. Without explicitly checking for this, the Pix[i:] expression below can panic.

	if r.Empty() {
		return &RGBA{}
	}
	i := p.PixOffset(r.Min.X, r.Min.Y)
	return &RGBA{
		Pix:    p.Pix[i:],
		Stride: p.Stride,
		Rect:   r,
	}
}

Opaque scans the entire image and reports whether it is fully opaque.

func (p *RGBA) Opaque() bool {
	if p.Rect.Empty() {
		return true
	}
	i0, i1 := 3, p.Rect.Dx()*4
	for y := p.Rect.Min.Y; y < p.Rect.Max.Y; y++ {
		for i := i0; i < i1; i += 4 {
			if p.Pix[i] != 0xff {
				return false
			}
		}
		i0 += p.Stride
		i1 += p.Stride
	}
	return true
}

NewRGBA returns a new RGBA image with the given bounds.

func NewRGBA(r Rectangle) *RGBA {
	return &RGBA{
		Pix:    make([]uint8, pixelBufferLength(4, r, "RGBA")),
		Stride: 4 * r.Dx(),
		Rect:   r,
	}
}

RGBA64 is an in-memory image whose At method returns color.RGBA64 values.

Pix holds the image's pixels, in R, G, B, A order and big-endian format. The pixel at (x, y) starts at Pix[(y-Rect.Min.Y)*Stride + (x-Rect.Min.X)*8].

Stride is the Pix stride (in bytes) between vertically adjacent pixels.

Rect is the image's bounds.

	Rect Rectangle
}

func (p *RGBA64) ColorModel() color.Model { return color.RGBA64Model }

func (p *RGBA64) Bounds() Rectangle { return p.Rect }

func (p *RGBA64) At(x, y int) color.Color {
	return p.RGBA64At(x, y)
}

func (p *RGBA64) RGBA64At(x, y int) color.RGBA64 {
	if !(Point{x, y}.In(p.Rect)) {
		return color.RGBA64{}
	}
	i := p.PixOffset(x, y)
	s := p.Pix[i : i+8 : i+8] // Small cap improves performance, see https://golang.org/issue/27857
	return color.RGBA64{
		uint16(s[0])<<8 | uint16(s[1]),
		uint16(s[2])<<8 | uint16(s[3]),
		uint16(s[4])<<8 | uint16(s[5]),
		uint16(s[6])<<8 | uint16(s[7]),
	}
}

PixOffset returns the index of the first element of Pix that corresponds to the pixel at (x, y).

func (p *RGBA64) PixOffset(x, y int) int {
	return (y-p.Rect.Min.Y)*p.Stride + (x-p.Rect.Min.X)*8
}

func (p *RGBA64) Set(x, y int, c color.Color) {
	if !(Point{x, y}.In(p.Rect)) {
		return
	}
	i := p.PixOffset(x, y)
	c1 := color.RGBA64Model.Convert(c).(color.RGBA64)
	s := p.Pix[i : i+8 : i+8] // Small cap improves performance, see https://golang.org/issue/27857
	s[0] = uint8(c1.R >> 8)
	s[1] = uint8(c1.R)
	s[2] = uint8(c1.G >> 8)
	s[3] = uint8(c1.G)
	s[4] = uint8(c1.B >> 8)
	s[5] = uint8(c1.B)
	s[6] = uint8(c1.A >> 8)
	s[7] = uint8(c1.A)
}

func (p *RGBA64) SetRGBA64(x, y int, c color.RGBA64) {
	if !(Point{x, y}.In(p.Rect)) {
		return
	}
	i := p.PixOffset(x, y)
	s := p.Pix[i : i+8 : i+8] // Small cap improves performance, see https://golang.org/issue/27857
	s[0] = uint8(c.R >> 8)
	s[1] = uint8(c.R)
	s[2] = uint8(c.G >> 8)
	s[3] = uint8(c.G)
	s[4] = uint8(c.B >> 8)
	s[5] = uint8(c.B)
	s[6] = uint8(c.A >> 8)
	s[7] = uint8(c.A)
}

SubImage returns an image representing the portion of the image p visible through r. The returned value shares pixels with the original image.

func (p *RGBA64) SubImage(r Rectangle) Image {

	if r.Empty() {
		return &RGBA64{}
	}
	i := p.PixOffset(r.Min.X, r.Min.Y)
	return &RGBA64{
		Pix:    p.Pix[i:],
		Stride: p.Stride,
		Rect:   r,
	}
}

Opaque scans the entire image and reports whether it is fully opaque.

func (p *RGBA64) Opaque() bool {
	if p.Rect.Empty() {
		return true
	}
	i0, i1 := 6, p.Rect.Dx()*8
	for y := p.Rect.Min.Y; y < p.Rect.Max.Y; y++ {
		for i := i0; i < i1; i += 8 {
			if p.Pix[i+0] != 0xff || p.Pix[i+1] != 0xff {
				return false
			}
		}
		i0 += p.Stride
		i1 += p.Stride
	}
	return true
}

NewRGBA64 returns a new RGBA64 image with the given bounds.

func NewRGBA64(r Rectangle) *RGBA64 {
	return &RGBA64{
		Pix:    make([]uint8, pixelBufferLength(8, r, "RGBA64")),
		Stride: 8 * r.Dx(),
		Rect:   r,
	}
}

NRGBA is an in-memory image whose At method returns color.NRGBA values.

Pix holds the image's pixels, in R, G, B, A order. The pixel at (x, y) starts at Pix[(y-Rect.Min.Y)*Stride + (x-Rect.Min.X)*4].

Stride is the Pix stride (in bytes) between vertically adjacent pixels.

Rect is the image's bounds.

	Rect Rectangle
}

func (p *NRGBA) ColorModel() color.Model { return color.NRGBAModel }

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

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

func (p *NRGBA) NRGBAAt(x, y int) color.NRGBA {
	if !(Point{x, y}.In(p.Rect)) {
		return color.NRGBA{}
	}
	i := p.PixOffset(x, y)
	s := p.Pix[i : i+4 : i+4] // Small cap improves performance, see https://golang.org/issue/27857
	return color.NRGBA{s[0], s[1], s[2], s[3]}
}

PixOffset returns the index of the first element of Pix that corresponds to the pixel at (x, y).

func (p *NRGBA) PixOffset(x, y int) int {
	return (y-p.Rect.Min.Y)*p.Stride + (x-p.Rect.Min.X)*4
}

func (p *NRGBA) Set(x, y int, c color.Color) {
	if !(Point{x, y}.In(p.Rect)) {
		return
	}
	i := p.PixOffset(x, y)
	c1 := color.NRGBAModel.Convert(c).(color.NRGBA)
	s := p.Pix[i : i+4 : i+4] // Small cap improves performance, see https://golang.org/issue/27857
	s[0] = c1.R
	s[1] = c1.G
	s[2] = c1.B
	s[3] = c1.A
}

func (p *NRGBA) SetNRGBA(x, y int, c color.NRGBA) {
	if !(Point{x, y}.In(p.Rect)) {
		return
	}
	i := p.PixOffset(x, y)
	s := p.Pix[i : i+4 : i+4] // Small cap improves performance, see https://golang.org/issue/27857
	s[0] = c.R
	s[1] = c.G
	s[2] = c.B
	s[3] = c.A
}

SubImage returns an image representing the portion of the image p visible through r. The returned value shares pixels with the original image.

func (p *NRGBA) SubImage(r Rectangle) Image {

	if r.Empty() {
		return &NRGBA{}
	}
	i := p.PixOffset(r.Min.X, r.Min.Y)
	return &NRGBA{
		Pix:    p.Pix[i:],
		Stride: p.Stride,
		Rect:   r,
	}
}

Opaque scans the entire image and reports whether it is fully opaque.

func (p *NRGBA) Opaque() bool {
	if p.Rect.Empty() {
		return true
	}
	i0, i1 := 3, p.Rect.Dx()*4
	for y := p.Rect.Min.Y; y < p.Rect.Max.Y; y++ {
		for i := i0; i < i1; i += 4 {
			if p.Pix[i] != 0xff {
				return false
			}
		}
		i0 += p.Stride
		i1 += p.Stride
	}
	return true
}

NewNRGBA returns a new NRGBA image with the given bounds.

func NewNRGBA(r Rectangle) *NRGBA {
	return &NRGBA{
		Pix:    make([]uint8, pixelBufferLength(4, r, "NRGBA")),
		Stride: 4 * r.Dx(),
		Rect:   r,
	}
}

NRGBA64 is an in-memory image whose At method returns color.NRGBA64 values.

Pix holds the image's pixels, in R, G, B, A order and big-endian format. The pixel at (x, y) starts at Pix[(y-Rect.Min.Y)*Stride + (x-Rect.Min.X)*8].

Stride is the Pix stride (in bytes) between vertically adjacent pixels.

Rect is the image's bounds.

	Rect Rectangle
}

func (p *NRGBA64) ColorModel() color.Model { return color.NRGBA64Model }

func (p *NRGBA64) Bounds() Rectangle { return p.Rect }

func (p *NRGBA64) At(x, y int) color.Color {
	return p.NRGBA64At(x, y)
}

func (p *NRGBA64) NRGBA64At(x, y int) color.NRGBA64 {
	if !(Point{x, y}.In(p.Rect)) {
		return color.NRGBA64{}
	}
	i := p.PixOffset(x, y)
	s := p.Pix[i : i+8 : i+8] // Small cap improves performance, see https://golang.org/issue/27857
	return color.NRGBA64{
		uint16(s[0])<<8 | uint16(s[1]),
		uint16(s[2])<<8 | uint16(s[3]),
		uint16(s[4])<<8 | uint16(s[5]),
		uint16(s[6])<<8 | uint16(s[7]),
	}
}

PixOffset returns the index of the first element of Pix that corresponds to the pixel at (x, y).

func (p *NRGBA64) PixOffset(x, y int) int {
	return (y-p.Rect.Min.Y)*p.Stride + (x-p.Rect.Min.X)*8
}

func (p *NRGBA64) Set(x, y int, c color.Color) {
	if !(Point{x, y}.In(p.Rect)) {
		return
	}
	i := p.PixOffset(x, y)
	c1 := color.NRGBA64Model.Convert(c).(color.NRGBA64)
	s := p.Pix[i : i+8 : i+8] // Small cap improves performance, see https://golang.org/issue/27857
	s[0] = uint8(c1.R >> 8)
	s[1] = uint8(c1.R)
	s[2] = uint8(c1.G >> 8)
	s[3] = uint8(c1.G)
	s[4] = uint8(c1.B >> 8)
	s[5] = uint8(c1.B)
	s[6] = uint8(c1.A >> 8)
	s[7] = uint8(c1.A)
}

func (p *NRGBA64) SetNRGBA64(x, y int, c color.NRGBA64) {
	if !(Point{x, y}.In(p.Rect)) {
		return
	}
	i := p.PixOffset(x, y)
	s := p.Pix[i : i+8 : i+8] // Small cap improves performance, see https://golang.org/issue/27857
	s[0] = uint8(c.R >> 8)
	s[1] = uint8(c.R)
	s[2] = uint8(c.G >> 8)
	s[3] = uint8(c.G)
	s[4] = uint8(c.B >> 8)
	s[5] = uint8(c.B)
	s[6] = uint8(c.A >> 8)
	s[7] = uint8(c.A)
}

SubImage returns an image representing the portion of the image p visible through r. The returned value shares pixels with the original image.

func (p *NRGBA64) SubImage(r Rectangle) Image {

	if r.Empty() {
		return &NRGBA64{}
	}
	i := p.PixOffset(r.Min.X, r.Min.Y)
	return &NRGBA64{
		Pix:    p.Pix[i:],
		Stride: p.Stride,
		Rect:   r,
	}
}

Opaque scans the entire image and reports whether it is fully opaque.

func (p *NRGBA64) Opaque() bool {
	if p.Rect.Empty() {
		return true
	}
	i0, i1 := 6, p.Rect.Dx()*8
	for y := p.Rect.Min.Y; y < p.Rect.Max.Y; y++ {
		for i := i0; i < i1; i += 8 {
			if p.Pix[i+0] != 0xff || p.Pix[i+1] != 0xff {
				return false
			}
		}
		i0 += p.Stride
		i1 += p.Stride
	}
	return true
}

NewNRGBA64 returns a new NRGBA64 image with the given bounds.

func NewNRGBA64(r Rectangle) *NRGBA64 {
	return &NRGBA64{
		Pix:    make([]uint8, pixelBufferLength(8, r, "NRGBA64")),
		Stride: 8 * r.Dx(),
		Rect:   r,
	}
}

Alpha is an in-memory image whose At method returns color.Alpha values.

Pix holds the image's pixels, as alpha values. The pixel at (x, y) starts at Pix[(y-Rect.Min.Y)*Stride + (x-Rect.Min.X)*1].

Stride is the Pix stride (in bytes) between vertically adjacent pixels.

Rect is the image's bounds.

	Rect Rectangle
}

func (p *Alpha) ColorModel() color.Model { return color.AlphaModel }

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

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

func (p *Alpha) AlphaAt(x, y int) color.Alpha {
	if !(Point{x, y}.In(p.Rect)) {
		return color.Alpha{}
	}
	i := p.PixOffset(x, y)
	return color.Alpha{p.Pix[i]}
}

PixOffset returns the index of the first element of Pix that corresponds to the pixel at (x, y).

func (p *Alpha) PixOffset(x, y int) int {
	return (y-p.Rect.Min.Y)*p.Stride + (x-p.Rect.Min.X)*1
}

func (p *Alpha) Set(x, y int, c color.Color) {
	if !(Point{x, y}.In(p.Rect)) {
		return
	}
	i := p.PixOffset(x, y)
	p.Pix[i] = color.AlphaModel.Convert(c).(color.Alpha).A
}

func (p *Alpha) SetAlpha(x, y int, c color.Alpha) {
	if !(Point{x, y}.In(p.Rect)) {
		return
	}
	i := p.PixOffset(x, y)
	p.Pix[i] = c.A
}

SubImage returns an image representing the portion of the image p visible through r. The returned value shares pixels with the original image.

func (p *Alpha) SubImage(r Rectangle) Image {

	if r.Empty() {
		return &Alpha{}
	}
	i := p.PixOffset(r.Min.X, r.Min.Y)
	return &Alpha{
		Pix:    p.Pix[i:],
		Stride: p.Stride,
		Rect:   r,
	}
}

Opaque scans the entire image and reports whether it is fully opaque.

func (p *Alpha) Opaque() bool {
	if p.Rect.Empty() {
		return true
	}
	i0, i1 := 0, p.Rect.Dx()
	for y := p.Rect.Min.Y; y < p.Rect.Max.Y; y++ {
		for i := i0; i < i1; i++ {
			if p.Pix[i] != 0xff {
				return false
			}
		}
		i0 += p.Stride
		i1 += p.Stride
	}
	return true
}

NewAlpha returns a new Alpha image with the given bounds.

func NewAlpha(r Rectangle) *Alpha {
	return &Alpha{
		Pix:    make([]uint8, pixelBufferLength(1, r, "Alpha")),
		Stride: 1 * r.Dx(),
		Rect:   r,
	}
}

Alpha16 is an in-memory image whose At method returns color.Alpha16 values.

Pix holds the image's pixels, as alpha values in big-endian format. The pixel at (x, y) starts at Pix[(y-Rect.Min.Y)*Stride + (x-Rect.Min.X)*2].

Stride is the Pix stride (in bytes) between vertically adjacent pixels.

Rect is the image's bounds.

	Rect Rectangle
}

func (p *Alpha16) ColorModel() color.Model { return color.Alpha16Model }

func (p *Alpha16) Bounds() Rectangle { return p.Rect }

func (p *Alpha16) At(x, y int) color.Color {
	return p.Alpha16At(x, y)
}

func (p *Alpha16) Alpha16At(x, y int) color.Alpha16 {
	if !(Point{x, y}.In(p.Rect)) {
		return color.Alpha16{}
	}
	i := p.PixOffset(x, y)
	return color.Alpha16{uint16(p.Pix[i+0])<<8 | uint16(p.Pix[i+1])}
}

PixOffset returns the index of the first element of Pix that corresponds to the pixel at (x, y).

func (p *Alpha16) PixOffset(x, y int) int {
	return (y-p.Rect.Min.Y)*p.Stride + (x-p.Rect.Min.X)*2
}

func (p *Alpha16) Set(x, y int, c color.Color) {
	if !(Point{x, y}.In(p.Rect)) {
		return
	}
	i := p.PixOffset(x, y)
	c1 := color.Alpha16Model.Convert(c).(color.Alpha16)
	p.Pix[i+0] = uint8(c1.A >> 8)
	p.Pix[i+1] = uint8(c1.A)
}

func (p *Alpha16) SetAlpha16(x, y int, c color.Alpha16) {
	if !(Point{x, y}.In(p.Rect)) {
		return
	}
	i := p.PixOffset(x, y)
	p.Pix[i+0] = uint8(c.A >> 8)
	p.Pix[i+1] = uint8(c.A)
}

SubImage returns an image representing the portion of the image p visible through r. The returned value shares pixels with the original image.

func (p *Alpha16) SubImage(r Rectangle) Image {

	if r.Empty() {
		return &Alpha16{}
	}
	i := p.PixOffset(r.Min.X, r.Min.Y)
	return &Alpha16{
		Pix:    p.Pix[i:],
		Stride: p.Stride,
		Rect:   r,
	}
}

Opaque scans the entire image and reports whether it is fully opaque.

func (p *Alpha16) Opaque() bool {
	if p.Rect.Empty() {
		return true
	}
	i0, i1 := 0, p.Rect.Dx()*2
	for y := p.Rect.Min.Y; y < p.Rect.Max.Y; y++ {
		for i := i0; i < i1; i += 2 {
			if p.Pix[i+0] != 0xff || p.Pix[i+1] != 0xff {
				return false
			}
		}
		i0 += p.Stride
		i1 += p.Stride
	}
	return true
}

NewAlpha16 returns a new Alpha16 image with the given bounds.

func NewAlpha16(r Rectangle) *Alpha16 {
	return &Alpha16{
		Pix:    make([]uint8, pixelBufferLength(2, r, "Alpha16")),
		Stride: 2 * r.Dx(),
		Rect:   r,
	}
}

Gray is an in-memory image whose At method returns color.Gray values.

Pix holds the image's pixels, as gray values. The pixel at (x, y) starts at Pix[(y-Rect.Min.Y)*Stride + (x-Rect.Min.X)*1].

Stride is the Pix stride (in bytes) between vertically adjacent pixels.

Rect is the image's bounds.

	Rect Rectangle
}

func (p *Gray) ColorModel() color.Model { return color.GrayModel }

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

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

func (p *Gray) GrayAt(x, y int) color.Gray {
	if !(Point{x, y}.In(p.Rect)) {
		return color.Gray{}
	}
	i := p.PixOffset(x, y)
	return color.Gray{p.Pix[i]}
}

PixOffset returns the index of the first element of Pix that corresponds to the pixel at (x, y).

func (p *Gray) PixOffset(x, y int) int {
	return (y-p.Rect.Min.Y)*p.Stride + (x-p.Rect.Min.X)*1
}

func (p *Gray) Set(x, y int, c color.Color) {
	if !(Point{x, y}.In(p.Rect)) {
		return
	}
	i := p.PixOffset(x, y)
	p.Pix[i] = color.GrayModel.Convert(c).(color.Gray).Y
}

func (p *Gray) SetGray(x, y int, c color.Gray) {
	if !(Point{x, y}.In(p.Rect)) {
		return
	}
	i := p.PixOffset(x, y)
	p.Pix[i] = c.Y
}

SubImage returns an image representing the portion of the image p visible through r. The returned value shares pixels with the original image.

func (p *Gray) SubImage(r Rectangle) Image {

	if r.Empty() {
		return &Gray{}
	}
	i := p.PixOffset(r.Min.X, r.Min.Y)
	return &Gray{
		Pix:    p.Pix[i:],
		Stride: p.Stride,
		Rect:   r,
	}
}

Opaque scans the entire image and reports whether it is fully opaque.

func (p *Gray) Opaque() bool {
	return true
}

NewGray returns a new Gray image with the given bounds.

func NewGray(r Rectangle) *Gray {
	return &Gray{
		Pix:    make([]uint8, pixelBufferLength(1, r, "Gray")),
		Stride: 1 * r.Dx(),
		Rect:   r,
	}
}

Gray16 is an in-memory image whose At method returns color.Gray16 values.

Pix holds the image's pixels, as gray values in big-endian format. The pixel at (x, y) starts at Pix[(y-Rect.Min.Y)*Stride + (x-Rect.Min.X)*2].

Stride is the Pix stride (in bytes) between vertically adjacent pixels.

Rect is the image's bounds.

	Rect Rectangle
}

func (p *Gray16) ColorModel() color.Model { return color.Gray16Model }

func (p *Gray16) Bounds() Rectangle { return p.Rect }

func (p *Gray16) At(x, y int) color.Color {
	return p.Gray16At(x, y)
}

func (p *Gray16) Gray16At(x, y int) color.Gray16 {
	if !(Point{x, y}.In(p.Rect)) {
		return color.Gray16{}
	}
	i := p.PixOffset(x, y)
	return color.Gray16{uint16(p.Pix[i+0])<<8 | uint16(p.Pix[i+1])}
}

PixOffset returns the index of the first element of Pix that corresponds to the pixel at (x, y).

func (p *Gray16) PixOffset(x, y int) int {
	return (y-p.Rect.Min.Y)*p.Stride + (x-p.Rect.Min.X)*2
}

func (p *Gray16) Set(x, y int, c color.Color) {
	if !(Point{x, y}.In(p.Rect)) {
		return
	}
	i := p.PixOffset(x, y)
	c1 := color.Gray16Model.Convert(c).(color.Gray16)
	p.Pix[i+0] = uint8(c1.Y >> 8)
	p.Pix[i+1] = uint8(c1.Y)
}

func (p *Gray16) SetGray16(x, y int, c color.Gray16) {
	if !(Point{x, y}.In(p.Rect)) {
		return
	}
	i := p.PixOffset(x, y)
	p.Pix[i+0] = uint8(c.Y >> 8)
	p.Pix[i+1] = uint8(c.Y)
}

SubImage returns an image representing the portion of the image p visible through r. The returned value shares pixels with the original image.

func (p *Gray16) SubImage(r Rectangle) Image {

	if r.Empty() {
		return &Gray16{}
	}
	i := p.PixOffset(r.Min.X, r.Min.Y)
	return &Gray16{
		Pix:    p.Pix[i:],
		Stride: p.Stride,
		Rect:   r,
	}
}

Opaque scans the entire image and reports whether it is fully opaque.

func (p *Gray16) Opaque() bool {
	return true
}

NewGray16 returns a new Gray16 image with the given bounds.

func NewGray16(r Rectangle) *Gray16 {
	return &Gray16{
		Pix:    make([]uint8, pixelBufferLength(2, r, "Gray16")),
		Stride: 2 * r.Dx(),
		Rect:   r,
	}
}

CMYK is an in-memory image whose At method returns color.CMYK values.

Pix holds the image's pixels, in C, M, Y, K order. The pixel at (x, y) starts at Pix[(y-Rect.Min.Y)*Stride + (x-Rect.Min.X)*4].

Stride is the Pix stride (in bytes) between vertically adjacent pixels.

Rect is the image's bounds.

	Rect Rectangle
}

func (p *CMYK) ColorModel() color.Model { return color.CMYKModel }

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

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

func (p *CMYK) CMYKAt(x, y int) color.CMYK {
	if !(Point{x, y}.In(p.Rect)) {
		return color.CMYK{}
	}
	i := p.PixOffset(x, y)
	s := p.Pix[i : i+4 : i+4] // Small cap improves performance, see https://golang.org/issue/27857
	return color.CMYK{s[0], s[1], s[2], s[3]}
}

PixOffset returns the index of the first element of Pix that corresponds to the pixel at (x, y).

func (p *CMYK) PixOffset(x, y int) int {
	return (y-p.Rect.Min.Y)*p.Stride + (x-p.Rect.Min.X)*4
}

func (p *CMYK) Set(x, y int, c color.Color) {
	if !(Point{x, y}.In(p.Rect)) {
		return
	}
	i := p.PixOffset(x, y)
	c1 := color.CMYKModel.Convert(c).(color.CMYK)
	s := p.Pix[i : i+4 : i+4] // Small cap improves performance, see https://golang.org/issue/27857
	s[0] = c1.C
	s[1] = c1.M
	s[2] = c1.Y
	s[3] = c1.K
}

func (p *CMYK) SetCMYK(x, y int, c color.CMYK) {
	if !(Point{x, y}.In(p.Rect)) {
		return
	}
	i := p.PixOffset(x, y)
	s := p.Pix[i : i+4 : i+4] // Small cap improves performance, see https://golang.org/issue/27857
	s[0] = c.C
	s[1] = c.M
	s[2] = c.Y
	s[3] = c.K
}

SubImage returns an image representing the portion of the image p visible through r. The returned value shares pixels with the original image.

func (p *CMYK) SubImage(r Rectangle) Image {

	if r.Empty() {
		return &CMYK{}
	}
	i := p.PixOffset(r.Min.X, r.Min.Y)
	return &CMYK{
		Pix:    p.Pix[i:],
		Stride: p.Stride,
		Rect:   r,
	}
}

Opaque scans the entire image and reports whether it is fully opaque.

func (p *CMYK) Opaque() bool {
	return true
}

NewCMYK returns a new CMYK image with the given bounds.

func NewCMYK(r Rectangle) *CMYK {
	return &CMYK{
		Pix:    make([]uint8, pixelBufferLength(4, r, "CMYK")),
		Stride: 4 * r.Dx(),
		Rect:   r,
	}
}

Paletted is an in-memory image of uint8 indices into a given palette.

Pix holds the image's pixels, as palette indices. The pixel at (x, y) starts at Pix[(y-Rect.Min.Y)*Stride + (x-Rect.Min.X)*1].

Stride is the Pix stride (in bytes) between vertically adjacent pixels.

Rect is the image's bounds.

Palette is the image's palette.

	Palette color.Palette
}

func (p *Paletted) ColorModel() color.Model { return p.Palette }

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

func (p *Paletted) At(x, y int) color.Color {
	if len(p.Palette) == 0 {
		return nil
	}
	if !(Point{x, y}.In(p.Rect)) {
		return p.Palette[0]
	}
	i := p.PixOffset(x, y)
	return p.Palette[p.Pix[i]]
}

PixOffset returns the index of the first element of Pix that corresponds to the pixel at (x, y).

func (p *Paletted) PixOffset(x, y int) int {
	return (y-p.Rect.Min.Y)*p.Stride + (x-p.Rect.Min.X)*1
}

func (p *Paletted) Set(x, y int, c color.Color) {
	if !(Point{x, y}.In(p.Rect)) {
		return
	}
	i := p.PixOffset(x, y)
	p.Pix[i] = uint8(p.Palette.Index(c))
}

func (p *Paletted) ColorIndexAt(x, y int) uint8 {
	if !(Point{x, y}.In(p.Rect)) {
		return 0
	}
	i := p.PixOffset(x, y)
	return p.Pix[i]
}

func (p *Paletted) SetColorIndex(x, y int, index uint8) {
	if !(Point{x, y}.In(p.Rect)) {
		return
	}
	i := p.PixOffset(x, y)
	p.Pix[i] = index
}

SubImage returns an image representing the portion of the image p visible through r. The returned value shares pixels with the original image.

func (p *Paletted) SubImage(r Rectangle) Image {

	if r.Empty() {
		return &Paletted{
			Palette: p.Palette,
		}
	}
	i := p.PixOffset(r.Min.X, r.Min.Y)
	return &Paletted{
		Pix:     p.Pix[i:],
		Stride:  p.Stride,
		Rect:    p.Rect.Intersect(r),
		Palette: p.Palette,
	}
}

Opaque scans the entire image and reports whether it is fully opaque.

func (p *Paletted) Opaque() bool {
	var present [256]bool
	i0, i1 := 0, p.Rect.Dx()
	for y := p.Rect.Min.Y; y < p.Rect.Max.Y; y++ {
		for _, c := range p.Pix[i0:i1] {
			present[c] = true
		}
		i0 += p.Stride
		i1 += p.Stride
	}
	for i, c := range p.Palette {
		if !present[i] {
			continue
		}
		_, _, _, a := c.RGBA()
		if a != 0xffff {
			return false
		}
	}
	return true
}

NewPaletted returns a new Paletted image with the given width, height and palette.

func NewPaletted(r Rectangle, p color.Palette) *Paletted {
	return &Paletted{
		Pix:     make([]uint8, pixelBufferLength(1, r, "Paletted")),
		Stride:  1 * r.Dx(),
		Rect:    r,
		Palette: p,
	}