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# Source file src/image/geom_test.go

## Documentation: image

```     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 image
6
7  import (
8  	"fmt"
9  	"testing"
10  )
11
12  func TestRectangle(t *testing.T) {
13  	// in checks that every point in f is in g.
14  	in := func(f, g Rectangle) error {
15  		if !f.In(g) {
16  			return fmt.Errorf("f=%s, f.In(%s): got false, want true", f, g)
17  		}
18  		for y := f.Min.Y; y < f.Max.Y; y++ {
19  			for x := f.Min.X; x < f.Max.X; x++ {
20  				p := Point{x, y}
21  				if !p.In(g) {
22  					return fmt.Errorf("p=%s, p.In(%s): got false, want true", p, g)
23  				}
24  			}
25  		}
26  		return nil
27  	}
28
29  	rects := []Rectangle{
30  		Rect(0, 0, 10, 10),
31  		Rect(10, 0, 20, 10),
32  		Rect(1, 2, 3, 4),
33  		Rect(4, 6, 10, 10),
34  		Rect(2, 3, 12, 5),
35  		Rect(-1, -2, 0, 0),
36  		Rect(-1, -2, 4, 6),
37  		Rect(-10, -20, 30, 40),
38  		Rect(8, 8, 8, 8),
39  		Rect(88, 88, 88, 88),
40  		Rect(6, 5, 4, 3),
41  	}
42
43  	// r.Eq(s) should be equivalent to every point in r being in s, and every
44  	// point in s being in r.
45  	for _, r := range rects {
46  		for _, s := range rects {
47  			got := r.Eq(s)
48  			want := in(r, s) == nil && in(s, r) == nil
49  			if got != want {
50  				t.Errorf("Eq: r=%s, s=%s: got %t, want %t", r, s, got, want)
51  			}
52  		}
53  	}
54
55  	// The intersection should be the largest rectangle a such that every point
56  	// in a is both in r and in s.
57  	for _, r := range rects {
58  		for _, s := range rects {
59  			a := r.Intersect(s)
60  			if err := in(a, r); err != nil {
61  				t.Errorf("Intersect: r=%s, s=%s, a=%s, a not in r: %v", r, s, a, err)
62  			}
63  			if err := in(a, s); err != nil {
64  				t.Errorf("Intersect: r=%s, s=%s, a=%s, a not in s: %v", r, s, a, err)
65  			}
66  			if isZero, overlaps := a == (Rectangle{}), r.Overlaps(s); isZero == overlaps {
67  				t.Errorf("Intersect: r=%s, s=%s, a=%s: isZero=%t same as overlaps=%t",
68  					r, s, a, isZero, overlaps)
69  			}
70  			largerThanA := [4]Rectangle{a, a, a, a}
71  			largerThanA[0].Min.X--
72  			largerThanA[1].Min.Y--
73  			largerThanA[2].Max.X++
74  			largerThanA[3].Max.Y++
75  			for i, b := range largerThanA {
76  				if b.Empty() {
77  					// b isn't actually larger than a.
78  					continue
79  				}
80  				if in(b, r) == nil && in(b, s) == nil {
81  					t.Errorf("Intersect: r=%s, s=%s, a=%s, b=%s, i=%d: intersection could be larger",
82  						r, s, a, b, i)
83  				}
84  			}
85  		}
86  	}
87
88  	// The union should be the smallest rectangle a such that every point in r
89  	// is in a and every point in s is in a.
90  	for _, r := range rects {
91  		for _, s := range rects {
92  			a := r.Union(s)
93  			if err := in(r, a); err != nil {
94  				t.Errorf("Union: r=%s, s=%s, a=%s, r not in a: %v", r, s, a, err)
95  			}
96  			if err := in(s, a); err != nil {
97  				t.Errorf("Union: r=%s, s=%s, a=%s, s not in a: %v", r, s, a, err)
98  			}
99  			if a.Empty() {
100  				// You can't get any smaller than a.
101  				continue
102  			}
103  			smallerThanA := [4]Rectangle{a, a, a, a}
104  			smallerThanA[0].Min.X++
105  			smallerThanA[1].Min.Y++
106  			smallerThanA[2].Max.X--
107  			smallerThanA[3].Max.Y--
108  			for i, b := range smallerThanA {
109  				if in(r, b) == nil && in(s, b) == nil {
110  					t.Errorf("Union: r=%s, s=%s, a=%s, b=%s, i=%d: union could be smaller",
111  						r, s, a, b, i)
112  				}
113  			}
114  		}
115  	}
116  }
117
```

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