geom_test.go

     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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