image_draw.go

     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
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