example_test.go

Documentation: golang.org/x/image/draw

     1  // Copyright 2015 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  package draw_test
     6  
     7  import (
     8  	"fmt"
     9  	"image"
    10  	"image/color"
    11  	"image/png"
    12  	"log"
    13  	"math"
    14  	"os"
    15  
    16  	"golang.org/x/image/draw"
    17  	"golang.org/x/image/math/f64"
    18  )
    19  
    20  func ExampleDraw() {
    21  	fSrc, err := os.Open("../testdata/blue-purple-pink.png")
    22  	if err != nil {
    23  		log.Fatal(err)
    24  	}
    25  	defer fSrc.Close()
    26  	src, err := png.Decode(fSrc)
    27  	if err != nil {
    28  		log.Fatal(err)
    29  	}
    30  
    31  	dst := image.NewRGBA(image.Rect(0, 0, 400, 300))
    32  	green := image.NewUniform(color.RGBA{0x00, 0x1f, 0x00, 0xff})
    33  	draw.Copy(dst, image.Point{}, green, dst.Bounds(), draw.Src, nil)
    34  	qs := []draw.Interpolator{
    35  		draw.NearestNeighbor,
    36  		draw.ApproxBiLinear,
    37  		draw.CatmullRom,
    38  	}
    39  	const cos60, sin60 = 0.5, 0.866025404
    40  	t := f64.Aff3{
    41  		+2 * cos60, -2 * sin60, 100,
    42  		+2 * sin60, +2 * cos60, 100,
    43  	}
    44  
    45  	draw.Copy(dst, image.Point{20, 30}, src, src.Bounds(), draw.Over, nil)
    46  	for i, q := range qs {
    47  		q.Scale(dst, image.Rect(200+10*i, 100*i, 600+10*i, 150+100*i), src, src.Bounds(), draw.Over, nil)
    48  	}
    49  	draw.NearestNeighbor.Transform(dst, t, src, src.Bounds(), draw.Over, nil)
    50  
    51  	red := image.NewNRGBA(image.Rect(0, 0, 16, 16))
    52  	for y := 0; y < 16; y++ {
    53  		for x := 0; x < 16; x++ {
    54  			red.SetNRGBA(x, y, color.NRGBA{
    55  				R: uint8(x * 0x11),
    56  				A: uint8(y * 0x11),
    57  			})
    58  		}
    59  	}
    60  	red.SetNRGBA(0, 0, color.NRGBA{0xff, 0xff, 0x00, 0xff})
    61  	red.SetNRGBA(15, 15, color.NRGBA{0xff, 0xff, 0x00, 0xff})
    62  
    63  	ops := []draw.Op{
    64  		draw.Over,
    65  		draw.Src,
    66  	}
    67  	for i, op := range ops {
    68  		dr := image.Rect(120+10*i, 150+60*i, 170+10*i, 200+60*i)
    69  		draw.NearestNeighbor.Scale(dst, dr, red, red.Bounds(), op, nil)
    70  		t := f64.Aff3{
    71  			+cos60, -sin60, float64(190 + 10*i),
    72  			+sin60, +cos60, float64(140 + 50*i),
    73  		}
    74  		draw.NearestNeighbor.Transform(dst, t, red, red.Bounds(), op, nil)
    75  	}
    76  
    77  	dr := image.Rect(0, 0, 128, 128)
    78  	checkerboard := image.NewAlpha(dr)
    79  	for y := dr.Min.Y; y < dr.Max.Y; y++ {
    80  		for x := dr.Min.X; x < dr.Max.X; x++ {
    81  			if (x/20)%2 == (y/20)%2 {
    82  				checkerboard.SetAlpha(x, y, color.Alpha{0xff})
    83  			}
    84  		}
    85  	}
    86  	sr := image.Rect(0, 0, 16, 16)
    87  	circle := image.NewAlpha(sr)
    88  	for y := sr.Min.Y; y < sr.Max.Y; y++ {
    89  		for x := sr.Min.X; x < sr.Max.X; x++ {
    90  			dx, dy := x-10, y-8
    91  			if d := 32 * math.Sqrt(float64(dx*dx)+float64(dy*dy)); d < 0xff {
    92  				circle.SetAlpha(x, y, color.Alpha{0xff - uint8(d)})
    93  			}
    94  		}
    95  	}
    96  	cyan := image.NewUniform(color.RGBA{0x00, 0xff, 0xff, 0xff})
    97  	draw.NearestNeighbor.Scale(dst, dr, cyan, sr, draw.Over, &draw.Options{
    98  		DstMask: checkerboard,
    99  		SrcMask: circle,
   100  	})
   101  
   102  	// Change false to true to write the resultant image to disk.
   103  	if false {
   104  		fDst, err := os.Create("out.png")
   105  		if err != nil {
   106  			log.Fatal(err)
   107  		}
   108  		defer fDst.Close()
   109  		err = png.Encode(fDst, dst)
   110  		if err != nil {
   111  			log.Fatal(err)
   112  		}
   113  	}
   114  
   115  	fmt.Printf("dst has bounds %v.\n", dst.Bounds())
   116  	// Output:
   117  	// dst has bounds (0,0)-(400,300).
   118  }
   119
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