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
5package draw_test
6
7import (
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
20func 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