1 // Copyright 2012 The Go Authors. All rights reserved. 2 // Use of this source code is governed by a BSD-style 3 // license that can be found in the LICENSE file. 4 5 // This file contains the code snippets included in "The Go image/draw package." 6 7 package main 8 9 import ( 10 "image" 11 "image/color" 12 "image/draw" 13 ) 14 15 func main() { 16 Color() 17 Rect() 18 RectAndScroll() 19 ConvAndCircle() 20 Glyph() 21 } 22 23 func Color() { 24 c := color.RGBA{255, 0, 255, 255} 25 r := image.Rect(0, 0, 640, 480) 26 dst := image.NewRGBA(r) 27 28 // ZERO OMIT 29 // image.ZP is the zero point -- the origin. 30 draw.Draw(dst, r, &image.Uniform{c}, image.ZP, draw.Src) 31 // STOP OMIT 32 33 // BLUE OMIT 34 m := image.NewRGBA(image.Rect(0, 0, 640, 480)) 35 blue := color.RGBA{0, 0, 255, 255} 36 draw.Draw(m, m.Bounds(), &image.Uniform{blue}, image.ZP, draw.Src) 37 // STOP OMIT 38 39 // RESET OMIT 40 draw.Draw(m, m.Bounds(), image.Transparent, image.ZP, draw.Src) 41 // STOP OMIT 42 } 43 44 func Rect() { 45 dst := image.NewRGBA(image.Rect(0, 0, 640, 480)) 46 sr := image.Rect(0, 0, 200, 200) 47 src := image.Black 48 dp := image.Point{100, 100} 49 50 // RECT OMIT 51 r := image.Rectangle{dp, dp.Add(sr.Size())} 52 draw.Draw(dst, r, src, sr.Min, draw.Src) 53 // STOP OMIT 54 } 55 56 func RectAndScroll() { 57 dst := image.NewRGBA(image.Rect(0, 0, 640, 480)) 58 sr := image.Rect(0, 0, 200, 200) 59 src := image.Black 60 dp := image.Point{100, 100} 61 62 // RECT2 OMIT 63 r := sr.Sub(sr.Min).Add(dp) 64 draw.Draw(dst, r, src, sr.Min, draw.Src) 65 // STOP OMIT 66 67 m := dst 68 69 // SCROLL OMIT 70 b := m.Bounds() 71 p := image.Pt(0, 20) 72 // Note that even though the second argument is b, 73 // the effective rectangle is smaller due to clipping. 74 draw.Draw(m, b, m, b.Min.Add(p), draw.Src) 75 dirtyRect := b.Intersect(image.Rect(b.Min.X, b.Max.Y-20, b.Max.X, b.Max.Y)) 76 // STOP OMIT 77 78 _ = dirtyRect // noop 79 } 80 81 func ConvAndCircle() { 82 src := image.NewRGBA(image.Rect(0, 0, 640, 480)) 83 dst := image.NewRGBA(image.Rect(0, 0, 640, 480)) 84 85 // CONV OMIT 86 b := src.Bounds() 87 m := image.NewRGBA(b) 88 draw.Draw(m, b, src, b.Min, draw.Src) 89 // STOP OMIT 90 91 p := image.Point{100, 100} 92 r := 50 93 94 // CIRCLE2 OMIT 95 draw.DrawMask(dst, dst.Bounds(), src, image.ZP, &circle{p, r}, image.ZP, draw.Over) 96 // STOP OMIT 97 } 98 99 func theGlyphImageForAFont() image.Image { 100 return image.NewRGBA(image.Rect(0, 0, 640, 480)) 101 } 102 103 func theBoundsFor(index int) image.Rectangle { 104 return image.Rect(0, 0, 32, 32) 105 } 106 107 func Glyph() { 108 p := image.Point{100, 100} 109 dst := image.NewRGBA(image.Rect(0, 0, 640, 480)) 110 glyphIndex := 42 111 112 // GLYPH OMIT 113 src := &image.Uniform{color.RGBA{0, 0, 255, 255}} 114 mask := theGlyphImageForAFont() 115 mr := theBoundsFor(glyphIndex) 116 draw.DrawMask(dst, mr.Sub(mr.Min).Add(p), src, image.ZP, mask, mr.Min, draw.Over) 117 // STOP OMIT 118 } 119 120 //CIRCLESTRUCT OMIT 121 type circle struct { 122 p image.Point 123 r int 124 } 125 126 func (c *circle) ColorModel() color.Model { 127 return color.AlphaModel 128 } 129 130 func (c *circle) Bounds() image.Rectangle { 131 return image.Rect(c.p.X-c.r, c.p.Y-c.r, c.p.X+c.r, c.p.Y+c.r) 132 } 133 134 func (c *circle) At(x, y int) color.Color { 135 xx, yy, rr := float64(x-c.p.X)+0.5, float64(y-c.p.Y)+0.5, float64(c.r) 136 if xx*xx+yy*yy < rr*rr { 137 return color.Alpha{255} 138 } 139 return color.Alpha{0} 140 } 141 142 //STOP OMIT 143
