package image

import "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

Security Considerations

The image package can be used to parse arbitrarily large images, which can cause resource exhaustion on machines which do not have enough memory to store them. When operating on arbitrary images, DecodeConfig should be called before Decode, so that the program can decide whether the image, as defined in the returned header, can be safely decoded with the available resources. A call to Decode which produces an extremely large image, as defined in the header returned by DecodeConfig, is not considered a security issue, regardless of whether the image is itself malformed or not. A call to DecodeConfig which returns a header which does not match the image returned by Decode may be considered a security issue, and should be reported per the [Go Security Policy](https://go.dev/security/policy).

Example 
package main

import (
	"encoding/base64"
	"fmt"
	"image"
	"log"
	"strings"

	// Package image/jpeg is not used explicitly in the code below,
	// but is imported for its initialization side-effect, which allows
	// image.Decode to understand JPEG formatted images. Uncomment these
	// two lines to also understand GIF and PNG images:
	// _ "image/gif"
	// _ "image/png"
	_ "image/jpeg"
)

func main() {
	// Decode the JPEG data. If reading from file, create a reader with
	//
	// reader, err := os.Open("testdata/video-001.q50.420.jpeg")
	// if err != nil {
	//     log.Fatal(err)
	// }
	// defer reader.Close()
	reader := base64.NewDecoder(base64.StdEncoding, strings.NewReader(data))
	m, _, err := image.Decode(reader)
	if err != nil {
		log.Fatal(err)
	}
	bounds := m.Bounds()

	// Calculate a 16-bin histogram for m's red, green, blue and alpha components.
	//
	// An image's bounds do not necessarily start at (0, 0), so the two loops start
	// at bounds.Min.Y and bounds.Min.X. Looping over Y first and X second is more
	// likely to result in better memory access patterns than X first and Y second.
	var histogram [16][4]int
	for y := bounds.Min.Y; y < bounds.Max.Y; y++ {
		for x := bounds.Min.X; x < bounds.Max.X; x++ {
			r, g, b, a := m.At(x, y).RGBA()
			// A color's RGBA method returns values in the range [0, 65535].
			// Shifting by 12 reduces this to the range [0, 15].
			histogram[r>>12][0]++
			histogram[g>>12][1]++
			histogram[b>>12][2]++
			histogram[a>>12][3]++
		}
	}

	// Print the results.
	fmt.Printf("%-14s %6s %6s %6s %6s\n", "bin", "red", "green", "blue", "alpha")
	for i, x := range histogram {
		fmt.Printf("0x%04x-0x%04x: %6d %6d %6d %6d\n", i<<12, (i+1)<<12-1, x[0], x[1], x[2], x[3])
	}
}

const data = `
/9j/4AAQSkZJRgABAQIAHAAcAAD/2wBDABALDA4MChAODQ4SERATGCgaGBYWGDEjJR0oOjM9PDkzODdA
SFxOQERXRTc4UG1RV19iZ2hnPk1xeXBkeFxlZ2P/2wBDARESEhgVGC8aGi9jQjhCY2NjY2NjY2NjY2Nj
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HwAAAQUBAQEBAQEAAAAAAAAAAAECAwQFBgcICQoL/8QAtRAAAgEDAwIEAwUFBAQAAAF9AQIDAAQRBRIh
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x8jJytLT1NXW19jZ2uHi4+Tl5ufo6erx8vP09fb3+Pn6/8QAHwEAAwEBAQEBAQEBAQAAAAAAAAECAwQF
BgcICQoL/8QAtREAAgECBAQDBAcFBAQAAQJ3AAECAxEEBSExBhJBUQdhcRMiMoEIFEKRobHBCSMzUvAV
YnLRChYkNOEl8RcYGRomJygpKjU2Nzg5OkNERUZHSElKU1RVVldYWVpjZGVmZ2hpanN0dXZ3eHl6goOE
hYaHiImKkpOUlZaXmJmaoqOkpaanqKmqsrO0tba3uLm6wsPExcbHyMnK0tPU1dbX2Nna4uPk5ebn6Onq
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cmgjilP3jSEZqS0IO/NGDnpUiocDg/McDjvV6HTPOdVWYgsM5KcfzzQ2JySM2jp6VYu7SWzmMUwG4cgj
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5XGTn29BV28jt7pPLuIVljPBBFVreYx+VbqAjycgt3x14zRcNOxGyVFHQkIc/wA61exyKLbuzjdZ046d
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ALy/zq1t96r3y4tT/vL/ADq4P3kRP4WSleTSFKkkKoCW4GaqNcMxIjXj1pxjKT0FKrGC1Nrw3vGrKkYz
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bSeNJ4xchni3DeqnBI+td7F4b0mKIRjT45VbktJlzk455+n6VtYzv2PNwFZWBHBGKVJDGVC54/nXQeMN
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itrSHFpGsUbndhRgc+g7VNIyfZJAoJZUbb3I46CtFJMylBo8sdWhmYMuCnylc9wef5VUT7+1chc5NS7h
sUZO5RtIPUH3pkBDOxxxmqM9TQtn+WilhHfHaik43KTG3Z4IyPyrNVjGCsZ+dmwv6V3cXhSG8sYpJLud
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oOxPU/8A68VVtbbRtMVntbePKDLTSHJH/Aj/AEqHTvE66rq72VugMMcbSGTnL4wMAfjT5n0HyW3L+s6b
baxaJBdzN+7bcrxkAhun0rz3VNCv7e7lgigknWI43xLu6jjIHTjtXqfkpPGVYsBkghTikgsYIN/lhgXb
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0HwyBXGeRjmrcUhMg2ghezd//rUUVcTKW5s2jZtY/QDaOKKKK8ip8bPRj8KP/9k=
`

Output:

bin               red  green   blue  alpha
0x0000-0x0fff:    364    790   7242      0
0x1000-0x1fff:    645   2967   1039      0
0x2000-0x2fff:   1072   2299    979      0
0x3000-0x3fff:    820   2266    980      0
0x4000-0x4fff:    537   1305    541      0
0x5000-0x5fff:    319    962    261      0
0x6000-0x6fff:    322    375    177      0
0x7000-0x7fff:    601    279    214      0
0x8000-0x8fff:   3478    227    273      0
0x9000-0x9fff:   2260    234    329      0
0xa000-0xafff:    921    282    373      0
0xb000-0xbfff:    321    335    397      0
0xc000-0xcfff:    229    388    298      0
0xd000-0xdfff:    260    414    277      0
0xe000-0xefff:    516    428    298      0
0xf000-0xffff:   2785   1899   1772  15450
Example (DecodeConfig) 
package main

import (
	"encoding/base64"
	"fmt"
	"image"
	"log"
	"strings"

	// Package image/jpeg is not used explicitly in the code below,
	// but is imported for its initialization side-effect, which allows
	// image.Decode to understand JPEG formatted images. Uncomment these
	// two lines to also understand GIF and PNG images:
	// _ "image/gif"
	// _ "image/png"
	_ "image/jpeg"
)

func main() {
	reader := base64.NewDecoder(base64.StdEncoding, strings.NewReader(data))
	config, format, err := image.DecodeConfig(reader)
	if err != nil {
		log.Fatal(err)
	}
	fmt.Println("Width:", config.Width, "Height:", config.Height, "Format:", format)
}

const data = `
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VwumgC+YiQyeVtZH567hzj8aSL949oGhE/2v5pJCDkksQwBHC4/+vXQ8LZ2uYxxCavY7us/xCcaBfn0h
b+VP0bnSrb94ZMJgOecj1rl/GfidUE2k2gy5+SeQjgA/wj3rlas2jdao48qrjLAGkSKPk4Gc1WMj92I+
lIJnU8OfxPWo5inBokmtQTmM4OOh71b0q6vbFmWCbaxHyqQGAP0PT8KhSTzVyo5ocSKA5VfTOTmqsmRd
pl99XjPzThzK3zOeOSeveirNmkgg/fIpYsTkYORxRXmzlTjJqx6EVUcU7mhkKCzdAK59QI9zYxtG1fYU
UVtgtmY4nZEa8Ak9aqFv3rfSiiu1nMeifDv/AJF+T/r4f+QrqqKKQwzQenNFFMCOKFIgNuThdoJ5OPSk
ubeK6t3gnXdG4wwziiii/UTKMOg6dbzJLFE4dSCP3rEdeOM8805tDsGMvySgSsS6rM6gk9eAcUUVftZt
3uyVGNthuq3Eei6DK8H7sRR7YuMgHtXkc8rzTNLM26RyWY+p70UVnLY0iEsUipG7rhZBlDkc1HgYoorM
0HwyBXGeRjmrcUhMg2ghezd//rUUVcTKW5s2jZtY/QDaOKKKK8ip8bPRj8KP/9k=
`

Index

Examples

Variables

var (
	// Black is an opaque black uniform image.
	Black = NewUniform(color.Black)
	// White is an opaque white uniform image.
	White = NewUniform(color.White)
	// Transparent is a fully transparent uniform image.
	Transparent = NewUniform(color.Transparent)
	// Opaque is a fully opaque uniform image.
	Opaque = NewUniform(color.Opaque)
)
var ErrFormat = errors.New("image: unknown format")

ErrFormat indicates that decoding encountered an unknown format.

Functions

func RegisterFormat

func RegisterFormat(name, magic string, decode func(io.Reader) (Image, error), decodeConfig func(io.Reader) (Config, error))

RegisterFormat registers an image format for use by Decode. Name is the name of the format, like "jpeg" or "png". Magic is the magic prefix that identifies the format's encoding. The magic string can contain "?" wildcards that each match any one byte. Decode is the function that decodes the encoded image. DecodeConfig is the function that decodes just its configuration.

Types

type Alpha

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

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

func NewAlpha

func NewAlpha(r Rectangle) *Alpha

NewAlpha returns a new Alpha image with the given bounds.

func (*Alpha) AlphaAt

func (p *Alpha) AlphaAt(x, y int) color.Alpha

func (*Alpha) At

func (p *Alpha) At(x, y int) color.Color

func (*Alpha) Bounds

func (p *Alpha) Bounds() Rectangle

func (*Alpha) ColorModel

func (p *Alpha) ColorModel() color.Model

func (*Alpha) Opaque

func (p *Alpha) Opaque() bool

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

func (*Alpha) PixOffset

func (p *Alpha) PixOffset(x, y int) int

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

func (*Alpha) RGBA64At

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

func (*Alpha) Set

func (p *Alpha) Set(x, y int, c color.Color)

func (*Alpha) SetAlpha

func (p *Alpha) SetAlpha(x, y int, c color.Alpha)

func (*Alpha) SetRGBA64

func (p *Alpha) SetRGBA64(x, y int, c color.RGBA64)

func (*Alpha) SubImage

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

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

type Alpha16

type Alpha16 struct {
	// 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].
	Pix []uint8
	// Stride is the Pix stride (in bytes) between vertically adjacent pixels.
	Stride int
	// Rect is the image's bounds.
	Rect Rectangle
}

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

func NewAlpha16

func NewAlpha16(r Rectangle) *Alpha16

NewAlpha16 returns a new Alpha16 image with the given bounds.

func (*Alpha16) Alpha16At

func (p *Alpha16) Alpha16At(x, y int) color.Alpha16

func (*Alpha16) At

func (p *Alpha16) At(x, y int) color.Color

func (*Alpha16) Bounds

func (p *Alpha16) Bounds() Rectangle

func (*Alpha16) ColorModel

func (p *Alpha16) ColorModel() color.Model

func (*Alpha16) Opaque

func (p *Alpha16) Opaque() bool

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

func (*Alpha16) PixOffset

func (p *Alpha16) PixOffset(x, y int) int

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

func (*Alpha16) RGBA64At

func (p *Alpha16) RGBA64At(x, y int) color.RGBA64

func (*Alpha16) Set

func (p *Alpha16) Set(x, y int, c color.Color)

func (*Alpha16) SetAlpha16

func (p *Alpha16) SetAlpha16(x, y int, c color.Alpha16)

func (*Alpha16) SetRGBA64

func (p *Alpha16) SetRGBA64(x, y int, c color.RGBA64)

func (*Alpha16) SubImage

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

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

type CMYK

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

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

func NewCMYK

func NewCMYK(r Rectangle) *CMYK

NewCMYK returns a new CMYK image with the given bounds.

func (*CMYK) At

func (p *CMYK) At(x, y int) color.Color

func (*CMYK) Bounds

func (p *CMYK) Bounds() Rectangle

func (*CMYK) CMYKAt

func (p *CMYK) CMYKAt(x, y int) color.CMYK

func (*CMYK) ColorModel

func (p *CMYK) ColorModel() color.Model

func (*CMYK) Opaque

func (p *CMYK) Opaque() bool

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

func (*CMYK) PixOffset

func (p *CMYK) PixOffset(x, y int) int

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

func (*CMYK) RGBA64At

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

func (*CMYK) Set

func (p *CMYK) Set(x, y int, c color.Color)

func (*CMYK) SetCMYK

func (p *CMYK) SetCMYK(x, y int, c color.CMYK)

func (*CMYK) SetRGBA64

func (p *CMYK) SetRGBA64(x, y int, c color.RGBA64)

func (*CMYK) SubImage

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

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

type Config

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

Config holds an image's color model and dimensions.

func DecodeConfig

func DecodeConfig(r io.Reader) (Config, string, error)

DecodeConfig decodes the color model and dimensions of an image that has been encoded in a registered format. The string returned is the format name used during format registration. Format registration is typically done by an init function in the codec-specific package.

type Gray

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

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

func NewGray

func NewGray(r Rectangle) *Gray

NewGray returns a new Gray image with the given bounds.

func (*Gray) At

func (p *Gray) At(x, y int) color.Color

func (*Gray) Bounds

func (p *Gray) Bounds() Rectangle

func (*Gray) ColorModel

func (p *Gray) ColorModel() color.Model

func (*Gray) GrayAt

func (p *Gray) GrayAt(x, y int) color.Gray

func (*Gray) Opaque

func (p *Gray) Opaque() bool

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

func (*Gray) PixOffset

func (p *Gray) PixOffset(x, y int) int

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

func (*Gray) RGBA64At

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

func (*Gray) Set

func (p *Gray) Set(x, y int, c color.Color)

func (*Gray) SetGray

func (p *Gray) SetGray(x, y int, c color.Gray)

func (*Gray) SetRGBA64

func (p *Gray) SetRGBA64(x, y int, c color.RGBA64)

func (*Gray) SubImage

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

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

type Gray16

type Gray16 struct {
	// 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].
	Pix []uint8
	// Stride is the Pix stride (in bytes) between vertically adjacent pixels.
	Stride int
	// Rect is the image's bounds.
	Rect Rectangle
}

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

func NewGray16

func NewGray16(r Rectangle) *Gray16

NewGray16 returns a new Gray16 image with the given bounds.

func (*Gray16) At

func (p *Gray16) At(x, y int) color.Color

func (*Gray16) Bounds

func (p *Gray16) Bounds() Rectangle

func (*Gray16) ColorModel

func (p *Gray16) ColorModel() color.Model

func (*Gray16) Gray16At

func (p *Gray16) Gray16At(x, y int) color.Gray16

func (*Gray16) Opaque

func (p *Gray16) Opaque() bool

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

func (*Gray16) PixOffset

func (p *Gray16) PixOffset(x, y int) int

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

func (*Gray16) RGBA64At

func (p *Gray16) RGBA64At(x, y int) color.RGBA64

func (*Gray16) Set

func (p *Gray16) Set(x, y int, c color.Color)

func (*Gray16) SetGray16

func (p *Gray16) SetGray16(x, y int, c color.Gray16)

func (*Gray16) SetRGBA64

func (p *Gray16) SetRGBA64(x, y int, c color.RGBA64)

func (*Gray16) SubImage

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

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

type Image

type Image interface {
	// ColorModel returns the Image's color model.
	ColorModel() color.Model
	// Bounds returns the domain for which At can return non-zero color.
	// The bounds do not necessarily contain the point (0, 0).
	Bounds() Rectangle
	// 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
}

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

func Decode

func Decode(r io.Reader) (Image, string, error)

Decode decodes an image that has been encoded in a registered format. The string returned is the format name used during format registration. Format registration is typically done by an init function in the codec- specific package.

type NRGBA

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

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

func NewNRGBA

func NewNRGBA(r Rectangle) *NRGBA

NewNRGBA returns a new NRGBA image with the given bounds.

func (*NRGBA) At

func (p *NRGBA) At(x, y int) color.Color

func (*NRGBA) Bounds

func (p *NRGBA) Bounds() Rectangle

func (*NRGBA) ColorModel

func (p *NRGBA) ColorModel() color.Model

func (*NRGBA) NRGBAAt

func (p *NRGBA) NRGBAAt(x, y int) color.NRGBA

func (*NRGBA) Opaque

func (p *NRGBA) Opaque() bool

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

func (*NRGBA) PixOffset

func (p *NRGBA) PixOffset(x, y int) int

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

func (*NRGBA) RGBA64At

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

func (*NRGBA) Set

func (p *NRGBA) Set(x, y int, c color.Color)

func (*NRGBA) SetNRGBA

func (p *NRGBA) SetNRGBA(x, y int, c color.NRGBA)

func (*NRGBA) SetRGBA64

func (p *NRGBA) SetRGBA64(x, y int, c color.RGBA64)

func (*NRGBA) SubImage

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

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

type NRGBA64

type NRGBA64 struct {
	// 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].
	Pix []uint8
	// Stride is the Pix stride (in bytes) between vertically adjacent pixels.
	Stride int
	// Rect is the image's bounds.
	Rect Rectangle
}

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

func NewNRGBA64

func NewNRGBA64(r Rectangle) *NRGBA64

NewNRGBA64 returns a new NRGBA64 image with the given bounds.

func (*NRGBA64) At

func (p *NRGBA64) At(x, y int) color.Color

func (*NRGBA64) Bounds

func (p *NRGBA64) Bounds() Rectangle

func (*NRGBA64) ColorModel

func (p *NRGBA64) ColorModel() color.Model

func (*NRGBA64) NRGBA64At

func (p *NRGBA64) NRGBA64At(x, y int) color.NRGBA64

func (*NRGBA64) Opaque

func (p *NRGBA64) Opaque() bool

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

func (*NRGBA64) PixOffset

func (p *NRGBA64) PixOffset(x, y int) int

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

func (*NRGBA64) RGBA64At

func (p *NRGBA64) RGBA64At(x, y int) color.RGBA64

func (*NRGBA64) Set

func (p *NRGBA64) Set(x, y int, c color.Color)

func (*NRGBA64) SetNRGBA64

func (p *NRGBA64) SetNRGBA64(x, y int, c color.NRGBA64)

func (*NRGBA64) SetRGBA64

func (p *NRGBA64) SetRGBA64(x, y int, c color.RGBA64)

func (*NRGBA64) SubImage

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

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

type NYCbCrA

type NYCbCrA struct {
	YCbCr
	A       []uint8
	AStride int
}

NYCbCrA is an in-memory image of non-alpha-premultiplied Y'CbCr-with-alpha colors. A and AStride are analogous to the Y and YStride fields of the embedded YCbCr.

func NewNYCbCrA

func NewNYCbCrA(r Rectangle, subsampleRatio YCbCrSubsampleRatio) *NYCbCrA

NewNYCbCrA returns a new NYCbCrA image with the given bounds and subsample ratio.

func (*NYCbCrA) AOffset

func (p *NYCbCrA) AOffset(x, y int) int

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

func (*NYCbCrA) At

func (p *NYCbCrA) At(x, y int) color.Color

func (*NYCbCrA) ColorModel

func (p *NYCbCrA) ColorModel() color.Model

func (*NYCbCrA) NYCbCrAAt

func (p *NYCbCrA) NYCbCrAAt(x, y int) color.NYCbCrA

func (*NYCbCrA) Opaque

func (p *NYCbCrA) Opaque() bool

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

func (*NYCbCrA) RGBA64At

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

func (*NYCbCrA) SubImage

func (p *NYCbCrA) SubImage(r Rectangle) Image

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

type Paletted

type Paletted struct {
	// 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].
	Pix []uint8
	// Stride is the Pix stride (in bytes) between vertically adjacent pixels.
	Stride int
	// Rect is the image's bounds.
	Rect Rectangle
	// Palette is the image's palette.
	Palette color.Palette
}

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

func NewPaletted

func NewPaletted(r Rectangle, p color.Palette) *Paletted

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

func (*Paletted) At

func (p *Paletted) At(x, y int) color.Color

func (*Paletted) Bounds

func (p *Paletted) Bounds() Rectangle

func (*Paletted) ColorIndexAt

func (p *Paletted) ColorIndexAt(x, y int) uint8

func (*Paletted) ColorModel

func (p *Paletted) ColorModel() color.Model

func (*Paletted) Opaque

func (p *Paletted) Opaque() bool

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

func (*Paletted) PixOffset

func (p *Paletted) PixOffset(x, y int) int

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

func (*Paletted) RGBA64At

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

func (*Paletted) Set

func (p *Paletted) Set(x, y int, c color.Color)

func (*Paletted) SetColorIndex

func (p *Paletted) SetColorIndex(x, y int, index uint8)

func (*Paletted) SetRGBA64

func (p *Paletted) SetRGBA64(x, y int, c color.RGBA64)

func (*Paletted) SubImage

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

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

type PalettedImage

type PalettedImage interface {
	// ColorIndexAt returns the palette index of the pixel at (x, y).
	ColorIndexAt(x, y int) uint8
	Image
}

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.

type Point

type Point struct {
	X, Y int
}

A Point is an X, Y coordinate pair. The axes increase right and down. 

var ZP Point

ZP is the zero Point.

Deprecated: Use a literal image.Point instead.

func Pt

func Pt(X, Y int) Point

Pt is shorthand for Point{X, Y}.

func (Point) Add

func (p Point) Add(q Point) Point

Add returns the vector p+q.

func (Point) Div

func (p Point) Div(k int) Point

Div returns the vector p/k.

func (Point) Eq

func (p Point) Eq(q Point) bool

Eq reports whether p and q are equal.

func (Point) In

func (p Point) In(r Rectangle) bool

In reports whether p is in r.

func (Point) Mod

func (p Point) Mod(r Rectangle) Point

Mod returns the point q in r such that p.X-q.X is a multiple of r's width and p.Y-q.Y is a multiple of r's height.

func (Point) Mul

func (p Point) Mul(k int) Point

Mul returns the vector p*k.

func (Point) String

func (p Point) String() string

String returns a string representation of p like "(3,4)".

func (Point) Sub

func (p Point) Sub(q Point) Point

Sub returns the vector p-q.

type RGBA

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

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

func NewRGBA

func NewRGBA(r Rectangle) *RGBA

NewRGBA returns a new RGBA image with the given bounds.

func (*RGBA) At

func (p *RGBA) At(x, y int) color.Color

func (*RGBA) Bounds

func (p *RGBA) Bounds() Rectangle

func (*RGBA) ColorModel

func (p *RGBA) ColorModel() color.Model

func (*RGBA) Opaque

func (p *RGBA) Opaque() bool

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

func (*RGBA) PixOffset

func (p *RGBA) PixOffset(x, y int) int

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

func (*RGBA) RGBA64At

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

func (*RGBA) RGBAAt

func (p *RGBA) RGBAAt(x, y int) color.RGBA

func (*RGBA) Set

func (p *RGBA) Set(x, y int, c color.Color)

func (*RGBA) SetRGBA

func (p *RGBA) SetRGBA(x, y int, c color.RGBA)

func (*RGBA) SetRGBA64

func (p *RGBA) SetRGBA64(x, y int, c color.RGBA64)

func (*RGBA) SubImage

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

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

type RGBA64

type RGBA64 struct {
	// 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].
	Pix []uint8
	// Stride is the Pix stride (in bytes) between vertically adjacent pixels.
	Stride int
	// Rect is the image's bounds.
	Rect Rectangle
}

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

func NewRGBA64

func NewRGBA64(r Rectangle) *RGBA64

NewRGBA64 returns a new RGBA64 image with the given bounds.

func (*RGBA64) At

func (p *RGBA64) At(x, y int) color.Color

func (*RGBA64) Bounds

func (p *RGBA64) Bounds() Rectangle

func (*RGBA64) ColorModel

func (p *RGBA64) ColorModel() color.Model

func (*RGBA64) Opaque

func (p *RGBA64) Opaque() bool

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

func (*RGBA64) PixOffset

func (p *RGBA64) PixOffset(x, y int) int

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

func (*RGBA64) RGBA64At

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

func (*RGBA64) Set

func (p *RGBA64) Set(x, y int, c color.Color)

func (*RGBA64) SetRGBA64

func (p *RGBA64) SetRGBA64(x, y int, c color.RGBA64)

func (*RGBA64) SubImage

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

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

type RGBA64Image

type RGBA64Image interface {
	// RGBA64At returns the RGBA64 color of the pixel at (x, y). It is
	// equivalent to calling At(x, y).RGBA() and converting the resulting
	// 32-bit return values to a color.RGBA64, but it can avoid allocations
	// from converting concrete color types to the color.Color interface type.
	RGBA64At(x, y int) color.RGBA64
	Image
}

RGBA64Image is an Image whose pixels can be converted directly to a color.RGBA64.

type Rectangle

type Rectangle struct {
	Min, Max Point
}

A Rectangle contains the points with Min.X <= X < Max.X, Min.Y <= Y < Max.Y. It is well-formed if Min.X <= Max.X and likewise for Y. Points are always well-formed. A rectangle's methods always return well-formed outputs for well-formed inputs.

A Rectangle is also an Image whose bounds are the rectangle itself. At returns color.Opaque for points in the rectangle and color.Transparent otherwise. 

var ZR Rectangle

ZR is the zero Rectangle.

Deprecated: Use a literal image.Rectangle instead.

func Rect

func Rect(x0, y0, x1, y1 int) Rectangle

Rect is shorthand for Rectangle{Pt(x0, y0), Pt(x1, y1)}. The returned rectangle has minimum and maximum coordinates swapped if necessary so that it is well-formed.

func (Rectangle) Add

func (r Rectangle) Add(p Point) Rectangle

Add returns the rectangle r translated by p.

func (Rectangle) At

func (r Rectangle) At(x, y int) color.Color

At implements the Image interface.

func (Rectangle) Bounds

func (r Rectangle) Bounds() Rectangle

Bounds implements the Image interface.

func (Rectangle) Canon

func (r Rectangle) Canon() Rectangle

Canon returns the canonical version of r. The returned rectangle has minimum and maximum coordinates swapped if necessary so that it is well-formed.

func (Rectangle) ColorModel

func (r Rectangle) ColorModel() color.Model

ColorModel implements the Image interface.

func (Rectangle) Dx

func (r Rectangle) Dx() int

Dx returns r's width.

func (Rectangle) Dy

func (r Rectangle) Dy() int

Dy returns r's height.

func (Rectangle) Empty

func (r Rectangle) Empty() bool

Empty reports whether the rectangle contains no points.

func (Rectangle) Eq

func (r Rectangle) Eq(s Rectangle) bool

Eq reports whether r and s contain the same set of points. All empty rectangles are considered equal.

func (Rectangle) In

func (r Rectangle) In(s Rectangle) bool

In reports whether every point in r is in s.

func (Rectangle) Inset

func (r Rectangle) Inset(n int) Rectangle

Inset returns the rectangle r inset by n, which may be negative. If either of r's dimensions is less than 2*n then an empty rectangle near the center of r will be returned.

func (Rectangle) Intersect

func (r Rectangle) Intersect(s Rectangle) Rectangle

Intersect returns the largest rectangle contained by both r and s. If the two rectangles do not overlap then the zero rectangle will be returned.

func (Rectangle) Overlaps

func (r Rectangle) Overlaps(s Rectangle) bool

Overlaps reports whether r and s have a non-empty intersection.

func (Rectangle) RGBA64At

func (r Rectangle) RGBA64At(x, y int) color.RGBA64

RGBA64At implements the RGBA64Image interface.

func (Rectangle) Size

func (r Rectangle) Size() Point

Size returns r's width and height.

func (Rectangle) String

func (r Rectangle) String() string

String returns a string representation of r like "(3,4)-(6,5)".

func (Rectangle) Sub

func (r Rectangle) Sub(p Point) Rectangle

Sub returns the rectangle r translated by -p.

func (Rectangle) Union

func (r Rectangle) Union(s Rectangle) Rectangle

Union returns the smallest rectangle that contains both r and s.

type Uniform

type Uniform struct {
	C color.Color
}

Uniform is an infinite-sized Image of uniform color. It implements the color.Color, color.Model, and Image interfaces.

func NewUniform

func NewUniform(c color.Color) *Uniform

NewUniform returns a new Uniform image of the given color.

func (*Uniform) At

func (c *Uniform) At(x, y int) color.Color

func (*Uniform) Bounds

func (c *Uniform) Bounds() Rectangle

func (*Uniform) ColorModel

func (c *Uniform) ColorModel() color.Model

func (*Uniform) Convert

func (c *Uniform) Convert(color.Color) color.Color

func (*Uniform) Opaque

func (c *Uniform) Opaque() bool

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

func (*Uniform) RGBA

func (c *Uniform) RGBA() (r, g, b, a uint32)

func (*Uniform) RGBA64At

func (c *Uniform) RGBA64At(x, y int) color.RGBA64

type YCbCr

type YCbCr struct {
	Y, Cb, Cr      []uint8
	YStride        int
	CStride        int
	SubsampleRatio YCbCrSubsampleRatio
	Rect           Rectangle
}

YCbCr is an in-memory image of Y'CbCr colors. There is one Y sample per pixel, but each Cb and Cr sample can span one or more pixels. YStride is the Y slice index delta between vertically adjacent pixels. CStride is the Cb and Cr slice index delta between vertically adjacent pixels that map to separate chroma samples. It is not an absolute requirement, but YStride and len(Y) are typically multiples of 8, and: 

For 4:4:4, CStride == YStride/1 && len(Cb) == len(Cr) == len(Y)/1.
For 4:2:2, CStride == YStride/2 && len(Cb) == len(Cr) == len(Y)/2.
For 4:2:0, CStride == YStride/2 && len(Cb) == len(Cr) == len(Y)/4.
For 4:4:0, CStride == YStride/1 && len(Cb) == len(Cr) == len(Y)/2.
For 4:1:1, CStride == YStride/4 && len(Cb) == len(Cr) == len(Y)/4.
For 4:1:0, CStride == YStride/4 && len(Cb) == len(Cr) == len(Y)/8.

func NewYCbCr

func NewYCbCr(r Rectangle, subsampleRatio YCbCrSubsampleRatio) *YCbCr

NewYCbCr returns a new YCbCr image with the given bounds and subsample ratio.

func (*YCbCr) At

func (p *YCbCr) At(x, y int) color.Color

func (*YCbCr) Bounds

func (p *YCbCr) Bounds() Rectangle

func (*YCbCr) COffset

func (p *YCbCr) COffset(x, y int) int

COffset returns the index of the first element of Cb or Cr that corresponds to the pixel at (x, y).

func (*YCbCr) ColorModel

func (p *YCbCr) ColorModel() color.Model

func (*YCbCr) Opaque

func (p *YCbCr) Opaque() bool

func (*YCbCr) RGBA64At

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

func (*YCbCr) SubImage

func (p *YCbCr) SubImage(r Rectangle) Image

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

func (*YCbCr) YCbCrAt

func (p *YCbCr) YCbCrAt(x, y int) color.YCbCr

func (*YCbCr) YOffset

func (p *YCbCr) YOffset(x, y int) int

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

type YCbCrSubsampleRatio

type YCbCrSubsampleRatio int

YCbCrSubsampleRatio is the chroma subsample ratio used in a YCbCr image. 

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

func (YCbCrSubsampleRatio) String

func (s YCbCrSubsampleRatio) String() string

Directories

color Package color implements a basic color library.
draw Package draw provides image composition functions.
gif Package gif implements a GIF image decoder and encoder.
jpeg Package jpeg implements a JPEG image decoder and encoder.
png Package png implements a PNG image decoder and encoder.