Source file src/pkg/image/image.go

// Copyright 2009 The Go Authors. All rights reserved.
// Use of this source code is governed by a BSD-style
// license that can be found in the LICENSE file.

// The image package implements a basic 2-D image library.
package image

// An Image is a rectangular grid of Colors drawn from a ColorModel.
type Image interface {
    ColorModel() ColorModel
    Width() int
    Height() int
    // At(0, 0) returns the upper-left pixel of the grid.
    // At(Width()-1, Height()-1) returns the lower-right pixel.
    At(x, y int) Color
}

// An RGBA is an in-memory image backed by a 2-D slice of RGBAColor values.
type RGBA struct {
    // The Pixel field's indices are y first, then x, so that At(x, y) == Pixel[y][x].
    Pixel [][]RGBAColor
}

func (p *RGBA) ColorModel() ColorModel { return RGBAColorModel }

func (p *RGBA) Width() int {
    if len(p.Pixel) == 0 {
        return 0
    }
    return len(p.Pixel[0])
}

func (p *RGBA) Height() int { return len(p.Pixel) }

func (p *RGBA) At(x, y int) Color { return p.Pixel[y][x] }

func (p *RGBA) Set(x, y int, c Color) { p.Pixel[y][x] = toRGBAColor(c).(RGBAColor) }

// Opaque scans the entire image and returns whether or not it is fully opaque.
func (p *RGBA) Opaque() bool {
    h := len(p.Pixel)
    if h > 0 {
        w := len(p.Pixel[0])
        for y := 0; y < h; y++ {
            pix := p.Pixel[y]
            for x := 0; x < w; x++ {
                if pix[x].A != 0xff {
                    return false
                }
            }
        }
    }
    return true
}

// NewRGBA returns a new RGBA with the given width and height.
func NewRGBA(w, h int) *RGBA {
    buf := make([]RGBAColor, w*h)
    pix := make([][]RGBAColor, h)
    for y := range pix {
        pix[y] = buf[w*y : w*(y+1)]
    }
    return &RGBA{pix}
}

// An RGBA64 is an in-memory image backed by a 2-D slice of RGBA64Color values.
type RGBA64 struct {
    // The Pixel field's indices are y first, then x, so that At(x, y) == Pixel[y][x].
    Pixel [][]RGBA64Color
}

func (p *RGBA64) ColorModel() ColorModel { return RGBA64ColorModel }

func (p *RGBA64) Width() int {
    if len(p.Pixel) == 0 {
        return 0
    }
    return len(p.Pixel[0])
}

func (p *RGBA64) Height() int { return len(p.Pixel) }

func (p *RGBA64) At(x, y int) Color { return p.Pixel[y][x] }

func (p *RGBA64) Set(x, y int, c Color) { p.Pixel[y][x] = toRGBA64Color(c).(RGBA64Color) }

// Opaque scans the entire image and returns whether or not it is fully opaque.
func (p *RGBA64) Opaque() bool {
    h := len(p.Pixel)
    if h > 0 {
        w := len(p.Pixel[0])
        for y := 0; y < h; y++ {
            pix := p.Pixel[y]
            for x := 0; x < w; x++ {
                if pix[x].A != 0xffff {
                    return false
                }
            }
        }
    }
    return true
}

// NewRGBA64 returns a new RGBA64 with the given width and height.
func NewRGBA64(w, h int) *RGBA64 {
    buf := make([]RGBA64Color, w*h)
    pix := make([][]RGBA64Color, h)
    for y := range pix {
        pix[y] = buf[w*y : w*(y+1)]
    }
    return &RGBA64{pix}
}

// A NRGBA is an in-memory image backed by a 2-D slice of NRGBAColor values.
type NRGBA struct {
    // The Pixel field's indices are y first, then x, so that At(x, y) == Pixel[y][x].
    Pixel [][]NRGBAColor
}

func (p *NRGBA) ColorModel() ColorModel { return NRGBAColorModel }

func (p *NRGBA) Width() int {
    if len(p.Pixel) == 0 {
        return 0
    }
    return len(p.Pixel[0])
}

func (p *NRGBA) Height() int { return len(p.Pixel) }

func (p *NRGBA) At(x, y int) Color { return p.Pixel[y][x] }

func (p *NRGBA) Set(x, y int, c Color) { p.Pixel[y][x] = toNRGBAColor(c).(NRGBAColor) }

// Opaque scans the entire image and returns whether or not it is fully opaque.
func (p *NRGBA) Opaque() bool {
    h := len(p.Pixel)
    if h > 0 {
        w := len(p.Pixel[0])
        for y := 0; y < h; y++ {
            pix := p.Pixel[y]
            for x := 0; x < w; x++ {
                if pix[x].A != 0xff {
                    return false
                }
            }
        }
    }
    return true
}

// NewNRGBA returns a new NRGBA with the given width and height.
func NewNRGBA(w, h int) *NRGBA {
    buf := make([]NRGBAColor, w*h)
    pix := make([][]NRGBAColor, h)
    for y := range pix {
        pix[y] = buf[w*y : w*(y+1)]
    }
    return &NRGBA{pix}
}

// A NRGBA64 is an in-memory image backed by a 2-D slice of NRGBA64Color values.
type NRGBA64 struct {
    // The Pixel field's indices are y first, then x, so that At(x, y) == Pixel[y][x].
    Pixel [][]NRGBA64Color
}

func (p *NRGBA64) ColorModel() ColorModel { return NRGBA64ColorModel }

func (p *NRGBA64) Width() int {
    if len(p.Pixel) == 0 {
        return 0
    }
    return len(p.Pixel[0])
}

func (p *NRGBA64) Height() int { return len(p.Pixel) }

func (p *NRGBA64) At(x, y int) Color { return p.Pixel[y][x] }

func (p *NRGBA64) Set(x, y int, c Color) { p.Pixel[y][x] = toNRGBA64Color(c).(NRGBA64Color) }

// Opaque scans the entire image and returns whether or not it is fully opaque.
func (p *NRGBA64) Opaque() bool {
    h := len(p.Pixel)
    if h > 0 {
        w := len(p.Pixel[0])
        for y := 0; y < h; y++ {
            pix := p.Pixel[y]
            for x := 0; x < w; x++ {
                if pix[x].A != 0xffff {
                    return false
                }
            }
        }
    }
    return true
}

// NewNRGBA64 returns a new NRGBA64 with the given width and height.
func NewNRGBA64(w, h int) *NRGBA64 {
    buf := make([]NRGBA64Color, w*h)
    pix := make([][]NRGBA64Color, h)
    for y := range pix {
        pix[y] = buf[w*y : w*(y+1)]
    }
    return &NRGBA64{pix}
}

// An Alpha is an in-memory image backed by a 2-D slice of AlphaColor values.
type Alpha struct {
    // The Pixel field's indices are y first, then x, so that At(x, y) == Pixel[y][x].
    Pixel [][]AlphaColor
}

func (p *Alpha) ColorModel() ColorModel { return AlphaColorModel }

func (p *Alpha) Width() int {
    if len(p.Pixel) == 0 {
        return 0
    }
    return len(p.Pixel[0])
}

func (p *Alpha) Height() int { return len(p.Pixel) }

func (p *Alpha) At(x, y int) Color { return p.Pixel[y][x] }

func (p *Alpha) Set(x, y int, c Color) { p.Pixel[y][x] = toAlphaColor(c).(AlphaColor) }

// Opaque scans the entire image and returns whether or not it is fully opaque.
func (p *Alpha) Opaque() bool {
    h := len(p.Pixel)
    if h > 0 {
        w := len(p.Pixel[0])
        for y := 0; y < h; y++ {
            pix := p.Pixel[y]
            for x := 0; x < w; x++ {
                if pix[x].A != 0xff {
                    return false
                }
            }
        }
    }
    return true
}

// NewAlpha returns a new Alpha with the given width and height.
func NewAlpha(w, h int) *Alpha {
    buf := make([]AlphaColor, w*h)
    pix := make([][]AlphaColor, h)
    for y := range pix {
        pix[y] = buf[w*y : w*(y+1)]
    }
    return &Alpha{pix}
}

// An Alpha16 is an in-memory image backed by a 2-D slice of Alpha16Color values.
type Alpha16 struct {
    // The Pixel field's indices are y first, then x, so that At(x, y) == Pixel[y][x].
    Pixel [][]Alpha16Color
}

func (p *Alpha16) ColorModel() ColorModel { return Alpha16ColorModel }

func (p *Alpha16) Width() int {
    if len(p.Pixel) == 0 {
        return 0
    }
    return len(p.Pixel[0])
}

func (p *Alpha16) Height() int { return len(p.Pixel) }

func (p *Alpha16) At(x, y int) Color { return p.Pixel[y][x] }

func (p *Alpha16) Set(x, y int, c Color) { p.Pixel[y][x] = toAlpha16Color(c).(Alpha16Color) }

// Opaque scans the entire image and returns whether or not it is fully opaque.
func (p *Alpha16) Opaque() bool {
    h := len(p.Pixel)
    if h > 0 {
        w := len(p.Pixel[0])
        for y := 0; y < h; y++ {
            pix := p.Pixel[y]
            for x := 0; x < w; x++ {
                if pix[x].A != 0xffff {
                    return false
                }
            }
        }
    }
    return true
}

// NewAlpha16 returns a new Alpha16 with the given width and height.
func NewAlpha16(w, h int) *Alpha16 {
    buf := make([]Alpha16Color, w*h)
    pix := make([][]Alpha16Color, h)
    for y := range pix {
        pix[y] = buf[w*y : w*(y+1)]
    }
    return &Alpha16{pix}
}

// A PalettedColorModel represents a fixed palette of colors.
type PalettedColorModel []Color

func diff(a, b uint32) uint32 {
    if a > b {
        return a - b
    }
    return b - a
}

// Convert returns the palette color closest to c in Euclidean R,G,B space.
func (p PalettedColorModel) Convert(c Color) Color {
    if len(p) == 0 {
        return nil
    }
    cr, cg, cb, _ := c.RGBA()
    // Shift by 1 bit to avoid potential uint32 overflow in sum-squared-difference.
    cr >>= 1
    cg >>= 1
    cb >>= 1
    result := Color(nil)
    bestSSD := uint32(1<<32 - 1)
    for _, v := range p {
        vr, vg, vb, _ := v.RGBA()
        vr >>= 1
        vg >>= 1
        vb >>= 1
        dr, dg, db := diff(cr, vr), diff(cg, vg), diff(cb, vb)
        ssd := (dr * dr) + (dg * dg) + (db * db)
        if ssd < bestSSD {
            bestSSD = ssd
            result = v
        }
    }
    return result
}

// A Paletted is an in-memory image backed by a 2-D slice of uint8 values and a PalettedColorModel.
type Paletted struct {
    // The Pixel field's indices are y first, then x, so that At(x, y) == Palette[Pixel[y][x]].
    Pixel   [][]uint8
    Palette PalettedColorModel
}

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

func (p *Paletted) Width() int {
    if len(p.Pixel) == 0 {
        return 0
    }
    return len(p.Pixel[0])
}

func (p *Paletted) Height() int { return len(p.Pixel) }

func (p *Paletted) At(x, y int) Color { return p.Palette[p.Pixel[y][x]] }

func (p *Paletted) ColorIndexAt(x, y int) uint8 {
    return p.Pixel[y][x]
}

func (p *Paletted) SetColorIndex(x, y int, index uint8) {
    p.Pixel[y][x] = index
}

// Opaque scans the entire image and returns whether or not it is fully opaque.
func (p *Paletted) Opaque() bool {
    for _, c := range p.Palette {
        _, _, _, a := c.RGBA()
        if a != 0xffff {
            return false
        }
    }
    return true
}

// NewPaletted returns a new Paletted with the given width, height and palette.
func NewPaletted(w, h int, m PalettedColorModel) *Paletted {
    buf := make([]uint8, w*h)
    pix := make([][]uint8, h)
    for y := range pix {
        pix[y] = buf[w*y : w*(y+1)]
    }
    return &Paletted{pix, m}
}