image

package
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 Go to latest Published: Jun 1, 2013 License: BSD-3-Clause Imports: 5 Imported by: 0

Documentation

Overview

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: http://golang.org/doc/articles/image_package.html

Example 
package main

import (
	"fmt"
	"image"
	"log"
	"os"

	// 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() {
	// Open the file.
	file, err := os.Open("testdata/video-001.jpeg")
	if err != nil {
		log.Fatal(err)
	}
	defer file.Close()

	// Decode the image.
	m, _, err := image.Decode(file)
	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])
	}
}

Output:

bin               red  green   blue  alpha
0x0000-0x0fff:    471    819   7596      0
0x1000-0x1fff:    576   2892    726      0
0x2000-0x2fff:   1038   2330    943      0
0x3000-0x3fff:    883   2321   1014      0
0x4000-0x4fff:    501   1295    525      0
0x5000-0x5fff:    302    962    242      0
0x6000-0x6fff:    219    358    150      0
0x7000-0x7fff:    352    281    192      0
0x8000-0x8fff:   3688    216    246      0
0x9000-0x9fff:   2277    237    283      0
0xa000-0xafff:    971    254    357      0
0xb000-0xbfff:    317    306    429      0
0xc000-0xcfff:    203    402    401      0
0xd000-0xdfff:    256    394    241      0
0xe000-0xefff:    378    343    173      0
0xf000-0xffff:   3018   2040   1932  15450

Index

Examples

Constants

This section is empty.

Variables

View Source 
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)
)
View Source 
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 with the given bounds.

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 returns whether or not 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) 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) 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.Alpha64 values.

func NewAlpha16 

func NewAlpha16(r Rectangle) *Alpha16

NewAlpha16 returns a new Alpha16 with the given bounds.

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 returns whether or not 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) 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) 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 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 the init method of 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 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) Opaque 

func (p *Gray) Opaque() bool

Opaque scans the entire image and returns whether or not 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) 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) 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 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) Opaque 

func (p *Gray16) Opaque() bool

Opaque scans the entire image and returns whether or not 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) 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) 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 the init method of 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 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) Opaque 

func (p *NRGBA) Opaque() bool

Opaque scans the entire image and returns whether or not 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) 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) 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 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) Opaque 

func (p *NRGBA64) Opaque() bool

Opaque scans the entire image and returns whether or not 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) 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) 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 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 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 returns whether or not 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) 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) 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 PalettedColorModel p, then m.At(x, y) should be equivalent to p[m.ColorIndexAt(x, y)]. If m's color model is not a PalettedColorModel, 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.

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 returns whether p and q are equal.

func (Point) In 

func (p Point) In(r Rectangle) bool

In returns 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 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 returns whether or not 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) 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) 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 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 returns whether or not 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) 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 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. 

var ZR Rectangle

ZR is the zero Rectangle.

func Rect 

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

Rect is shorthand for Rectangle{Pt(x0, y0), Pt(x1, y1)}.

func (Rectangle) Add 

func (r Rectangle) Add(p Point) Rectangle

Add returns the rectangle r translated by p.

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) 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 returns whether the rectangle contains no points.

func (Rectangle) Eq 

func (r Rectangle) Eq(s Rectangle) bool

Eq returns whether r and s are equal.

func (Rectangle) In 

func (r Rectangle) In(s Rectangle) bool

In returns 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 returns whether r and s have a non-empty intersection.

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

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 returns whether or not it is fully opaque.

func (*Uniform) RGBA 

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

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.

func NewYCbCr 

func NewYCbCr(r Rectangle, subsampleRatio YCbCrSubsampleRatio) *YCbCr

NewYCbCr returns a new YCbCr 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) 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) 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
)

func (YCbCrSubsampleRatio) String 

func (s YCbCrSubsampleRatio) String() string

Source Files

View all Source files

Directories

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

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