Package draw

• import "image/draw"
• Overview
• Index
• Examples

Overview

Package draw provides image composition functions.

See "The Go image/draw package" for an introduction to this package: https://golang.org/doc/articles/image_draw.html

Index

• func Draw(dst Image, r image.Rectangle, src image.Image, sp image.Point, op Op)
• func DrawMask(dst Image, r image.Rectangle, src image.Image, sp image.Point, mask image.Image, mp image.Point, op Op)
• type Drawer
• type Image
• type Op
• func (op Op) Draw(dst Image, r image.Rectangle, src image.Image, sp image.Point)
• type Quantizer

Package files

draw.go

func DrawSource

func Draw(dst Image, r image.Rectangle, src image.Image, sp image.Point, op Op)

Draw calls DrawMask with a nil mask.

func DrawMaskSource

func DrawMask(dst Image, r image.Rectangle, src image.Image, sp image.Point, mask image.Image, mp image.Point, op Op)

DrawMask aligns r.Min in dst with sp in src and mp in mask and then replaces the rectangle r in dst with the result of a Porter-Duff composition. A nil mask is treated as opaque.

type DrawerSource 1.2

Drawer contains the Draw method.

type Drawer interface {
    // Draw aligns r.Min in dst with sp in src and then replaces the
    // rectangle r in dst with the result of drawing src on dst.
    Draw(dst Image, r image.Rectangle, src image.Image, sp image.Point)
}

FloydSteinberg is a Drawer that is the Src Op with Floyd-Steinberg error diffusion.

var FloydSteinberg Drawer = floydSteinberg{}

Example (FloydSteinberg)

package main

import (
	"fmt"
	"image"
	"image/color"
	"image/draw"
	"math"
)

func main() {
	const width = 130
	const height = 50

	im := image.NewGray(image.Rectangle{Max: image.Point{X: width, Y: height}})
	for x := 0; x < width; x++ {
		for y := 0; y < height; y++ {
			dist := math.Sqrt(math.Pow(float64(x-width/2), 2)/3+math.Pow(float64(y-height/2), 2)) / (height / 1.5) * 255
			var gray uint8
			if dist > 255 {
				gray = 255
			} else {
				gray = uint8(dist)
			}
			im.SetGray(x, y, color.Gray{Y: 255 - gray})
		}
	}
	pi := image.NewPaletted(im.Bounds(), []color.Color{
		color.Gray{Y: 255},
		color.Gray{Y: 160},
		color.Gray{Y: 70},
		color.Gray{Y: 35},
		color.Gray{Y: 0},
	})

	draw.FloydSteinberg.Draw(pi, im.Bounds(), im, image.ZP)
	shade := []string{" ", "░", "▒", "▓", "█"}
	for i, p := range pi.Pix {
		fmt.Print(shade[p])
		if (i+1)%width == 0 {
			fmt.Print("\n")
		}
	}
}

type ImageSource

Image is an image.Image with a Set method to change a single pixel.

type Image interface {
    image.Image
    Set(x, y int, c color.Color)
}

type OpSource

Op is a Porter-Duff compositing operator.

type Op int

const (
    // Over specifies ``(src in mask) over dst''.
    Over Op = iota
    // Src specifies ``src in mask''.
    Src
)

func (Op) DrawSource 1.2

func (op Op) Draw(dst Image, r image.Rectangle, src image.Image, sp image.Point)

Draw implements the Drawer interface by calling the Draw function with this Op.

type QuantizerSource 1.2

Quantizer produces a palette for an image.

type Quantizer interface {
    // Quantize appends up to cap(p) - len(p) colors to p and returns the
    // updated palette suitable for converting m to a paletted image.
    Quantize(p color.Palette, m image.Image) color.Palette
}