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Package color

Overview

Package color implements a basic color library.

Index

Package files

color.go ycbcr.go

Variables

Standard colors.

var (
        Black       = Gray16{0}
        White       = Gray16{0xffff}
        Transparent = Alpha16{0}
        Opaque      = Alpha16{0xffff}
)

func CMYKToRGBSource

func CMYKToRGB(c, m, y, k uint8) (uint8, uint8, uint8)

CMYKToRGB converts a CMYK quadruple to an RGB triple.

func RGBToCMYKSource

func RGBToCMYK(r, g, b uint8) (uint8, uint8, uint8, uint8)

RGBToCMYK converts an RGB triple to a CMYK quadruple.

func RGBToYCbCrSource

func RGBToYCbCr(r, g, b uint8) (uint8, uint8, uint8)

RGBToYCbCr converts an RGB triple to a Y'CbCr triple.

func YCbCrToRGBSource

func YCbCrToRGB(y, cb, cr uint8) (uint8, uint8, uint8)

YCbCrToRGB converts a Y'CbCr triple to an RGB triple.

type AlphaSource

Alpha represents an 8-bit alpha color.

type Alpha struct {
        A uint8
}

func (Alpha) RGBASource

func (c Alpha) RGBA() (r, g, b, a uint32)

type Alpha16Source

Alpha16 represents a 16-bit alpha color.

type Alpha16 struct {
        A uint16
}

func (Alpha16) RGBASource

func (c Alpha16) RGBA() (r, g, b, a uint32)

type CMYKSource

CMYK represents a fully opaque CMYK color, having 8 bits for each of cyan, magenta, yellow and black.

It is not associated with any particular color profile.

type CMYK struct {
        C, M, Y, K uint8
}

func (CMYK) RGBASource

func (c CMYK) RGBA() (uint32, uint32, uint32, uint32)

type ColorSource

Color can convert itself to alpha-premultiplied 16-bits per channel RGBA. The conversion may be lossy.

type Color interface {
        // RGBA returns the alpha-premultiplied red, green, blue and alpha values
        // for the color. Each value ranges within [0, 0xffff], but is represented
        // by a uint32 so that multiplying by a blend factor up to 0xffff will not
        // overflow.
        //
        // An alpha-premultiplied color component c has been scaled by alpha (a),
        // so has valid values 0 <= c <= a.
        RGBA() (r, g, b, a uint32)
}

type GraySource

Gray represents an 8-bit grayscale color.

type Gray struct {
        Y uint8
}

func (Gray) RGBASource

func (c Gray) RGBA() (r, g, b, a uint32)

type Gray16Source

Gray16 represents a 16-bit grayscale color.

type Gray16 struct {
        Y uint16
}

func (Gray16) RGBASource

func (c Gray16) RGBA() (r, g, b, a uint32)

type ModelSource

Model can convert any Color to one from its own color model. The conversion may be lossy.

type Model interface {
        Convert(c Color) Color
}

Models for the standard color types.

var (
        RGBAModel    Model = ModelFunc(rgbaModel)
        RGBA64Model  Model = ModelFunc(rgba64Model)
        NRGBAModel   Model = ModelFunc(nrgbaModel)
        NRGBA64Model Model = ModelFunc(nrgba64Model)
        AlphaModel   Model = ModelFunc(alphaModel)
        Alpha16Model Model = ModelFunc(alpha16Model)
        GrayModel    Model = ModelFunc(grayModel)
        Gray16Model  Model = ModelFunc(gray16Model)
)

CMYKModel is the Model for CMYK colors.

var CMYKModel Model = ModelFunc(cmykModel)

NYCbCrAModel is the Model for non-alpha-premultiplied Y'CbCr-with-alpha colors.

var NYCbCrAModel Model = ModelFunc(nYCbCrAModel)

YCbCrModel is the Model for Y'CbCr colors.

var YCbCrModel Model = ModelFunc(yCbCrModel)

func ModelFuncSource

func ModelFunc(f func(Color) Color) Model

ModelFunc returns a Model that invokes f to implement the conversion.

type NRGBASource

NRGBA represents a non-alpha-premultiplied 32-bit color.

type NRGBA struct {
        R, G, B, A uint8
}

func (NRGBA) RGBASource

func (c NRGBA) RGBA() (r, g, b, a uint32)

type NRGBA64Source

NRGBA64 represents a non-alpha-premultiplied 64-bit color, having 16 bits for each of red, green, blue and alpha.

type NRGBA64 struct {
        R, G, B, A uint16
}

func (NRGBA64) RGBASource

func (c NRGBA64) RGBA() (r, g, b, a uint32)

type NYCbCrASource

NYCbCrA represents a non-alpha-premultiplied Y'CbCr-with-alpha color, having 8 bits each for one luma, two chroma and one alpha component.

type NYCbCrA struct {
        YCbCr
        A uint8
}

func (NYCbCrA) RGBASource

func (c NYCbCrA) RGBA() (uint32, uint32, uint32, uint32)

type PaletteSource

Palette is a palette of colors.

type Palette []Color

func (Palette) ConvertSource

func (p Palette) Convert(c Color) Color

Convert returns the palette color closest to c in Euclidean R,G,B space.

func (Palette) IndexSource

func (p Palette) Index(c Color) int

Index returns the index of the palette color closest to c in Euclidean R,G,B,A space.

type RGBASource

RGBA represents a traditional 32-bit alpha-premultiplied color, having 8 bits for each of red, green, blue and alpha.

An alpha-premultiplied color component C has been scaled by alpha (A), so has valid values 0 <= C <= A.

type RGBA struct {
        R, G, B, A uint8
}

func (RGBA) RGBASource

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

type RGBA64Source

RGBA64 represents a 64-bit alpha-premultiplied color, having 16 bits for each of red, green, blue and alpha.

An alpha-premultiplied color component C has been scaled by alpha (A), so has valid values 0 <= C <= A.

type RGBA64 struct {
        R, G, B, A uint16
}

func (RGBA64) RGBASource

func (c RGBA64) RGBA() (r, g, b, a uint32)

type YCbCrSource

YCbCr represents a fully opaque 24-bit Y'CbCr color, having 8 bits each for one luma and two chroma components.

JPEG, VP8, the MPEG family and other codecs use this color model. Such codecs often use the terms YUV and Y'CbCr interchangeably, but strictly speaking, the term YUV applies only to analog video signals, and Y' (luma) is Y (luminance) after applying gamma correction.

Conversion between RGB and Y'CbCr is lossy and there are multiple, slightly different formulae for converting between the two. This package follows the JFIF specification at http://www.w3.org/Graphics/JPEG/jfif3.pdf.

type YCbCr struct {
        Y, Cb, Cr uint8
}

func (YCbCr) RGBASource

func (c YCbCr) RGBA() (uint32, uint32, uint32, uint32)

Subdirectories

Name Synopsis
..
palette Package palette provides standard color palettes.

© Google, Inc.
Licensed under the Creative Commons Attribution License 3.0.
https://golang.org/pkg/image/color/