version: 1.10

package draw

import "image/draw"

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

Examples

Package files

draw.go

func Draw 

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

Draw calls DrawMask with a nil mask.

func DrawMask 

  1. 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 Drawer 

  1. type Drawer interface {
  2.     // Draw aligns r.Min in dst with sp in src and then replaces the
  3.     // rectangle r in dst with the result of drawing src on dst.
  4.     Draw(dst Image, r image.Rectangle, src image.Image, sp image.Point)
  5. }

Drawer contains the Draw method.

  1. var FloydSteinberg Drawer = floydSteinberg{}

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

Example:

  1. const width = 130
  2. const height = 50
  4. im := image.NewGray(image.Rectangle{Max: image.Point{X: width, Y: height}})
  5. for x := 0; x < width; x++ {
  6.     for y := 0; y < height; y++ {
  7.         dist := math.Sqrt(math.Pow(float64(x-width/2), 2)/3+math.Pow(float64(y-height/2), 2)) / (height / 1.5) * 255
  8.         var gray uint8
  9.         if dist > 255 {
  10.             gray = 255
  11.         } else {
  12.             gray = uint8(dist)
  13.         }
  14.         im.SetGray(x, y, color.Gray{Y: 255 - gray})
  15.     }
  16. }
  17. pi := image.NewPaletted(im.Bounds(), []color.Color{
  18.     color.Gray{Y: 255},
  19.     color.Gray{Y: 160},
  20.     color.Gray{Y: 70},
  21.     color.Gray{Y: 35},
  22.     color.Gray{Y: 0},
  23. })
  25. draw.FloydSteinberg.Draw(pi, im.Bounds(), im, image.ZP)
  26. shade := []string{" ", "░", "▒", "▓", "█"}
  27. for i, p := range pi.Pix {
  28.     fmt.Print(shade[p])
  29.     if (i+1)%width == 0 {
  30.         fmt.Print("\n")
  31.     }
  32. }

type Image 

  1. type Image interface {
  2.     image.Image
  3.     Set(x, y int, c color.Color)
  4. }

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

type Op 

  1. type Op int

Op is a Porter-Duff compositing operator.

  1. const (
  2.     // Over specifies ``(src in mask) over dst''.
  3.     Over Op = iota
  4.     // Src specifies ``src in mask''.
  5.     Src
  6. )

func (Op) Draw 

  1. 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 Quantizer 

  1. type Quantizer interface {
  2.     // Quantize appends up to cap(p) - len(p) colors to p and returns the
  3.     // updated palette suitable for converting m to a paletted image.
  4.     Quantize(p color.Palette, m image.Image) color.Palette
  5. }

Quantizer produces a palette for an image.