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Source file src/image/geom_test.go

Documentation: image

  // Copyright 2015 The Go Authors. All rights reserved.
  // Use of this source code is governed by a BSD-style
  // license that can be found in the LICENSE file.
  
  package image
  
  import (
  	"fmt"
  	"testing"
  )
  
  func TestRectangle(t *testing.T) {
  	// in checks that every point in f is in g.
  	in := func(f, g Rectangle) error {
  		if !f.In(g) {
  			return fmt.Errorf("f=%s, f.In(%s): got false, want true", f, g)
  		}
  		for y := f.Min.Y; y < f.Max.Y; y++ {
  			for x := f.Min.X; x < f.Max.X; x++ {
  				p := Point{x, y}
  				if !p.In(g) {
  					return fmt.Errorf("p=%s, p.In(%s): got false, want true", p, g)
  				}
  			}
  		}
  		return nil
  	}
  
  	rects := []Rectangle{
  		Rect(0, 0, 10, 10),
  		Rect(10, 0, 20, 10),
  		Rect(1, 2, 3, 4),
  		Rect(4, 6, 10, 10),
  		Rect(2, 3, 12, 5),
  		Rect(-1, -2, 0, 0),
  		Rect(-1, -2, 4, 6),
  		Rect(-10, -20, 30, 40),
  		Rect(8, 8, 8, 8),
  		Rect(88, 88, 88, 88),
  		Rect(6, 5, 4, 3),
  	}
  
  	// r.Eq(s) should be equivalent to every point in r being in s, and every
  	// point in s being in r.
  	for _, r := range rects {
  		for _, s := range rects {
  			got := r.Eq(s)
  			want := in(r, s) == nil && in(s, r) == nil
  			if got != want {
  				t.Errorf("Eq: r=%s, s=%s: got %t, want %t", r, s, got, want)
  			}
  		}
  	}
  
  	// The intersection should be the largest rectangle a such that every point
  	// in a is both in r and in s.
  	for _, r := range rects {
  		for _, s := range rects {
  			a := r.Intersect(s)
  			if err := in(a, r); err != nil {
  				t.Errorf("Intersect: r=%s, s=%s, a=%s, a not in r: %v", r, s, a, err)
  			}
  			if err := in(a, s); err != nil {
  				t.Errorf("Intersect: r=%s, s=%s, a=%s, a not in s: %v", r, s, a, err)
  			}
  			if isZero, overlaps := a == (Rectangle{}), r.Overlaps(s); isZero == overlaps {
  				t.Errorf("Intersect: r=%s, s=%s, a=%s: isZero=%t same as overlaps=%t",
  					r, s, a, isZero, overlaps)
  			}
  			largerThanA := [4]Rectangle{a, a, a, a}
  			largerThanA[0].Min.X--
  			largerThanA[1].Min.Y--
  			largerThanA[2].Max.X++
  			largerThanA[3].Max.Y++
  			for i, b := range largerThanA {
  				if b.Empty() {
  					// b isn't actually larger than a.
  					continue
  				}
  				if in(b, r) == nil && in(b, s) == nil {
  					t.Errorf("Intersect: r=%s, s=%s, a=%s, b=%s, i=%d: intersection could be larger",
  						r, s, a, b, i)
  				}
  			}
  		}
  	}
  
  	// The union should be the smallest rectangle a such that every point in r
  	// is in a and every point in s is in a.
  	for _, r := range rects {
  		for _, s := range rects {
  			a := r.Union(s)
  			if err := in(r, a); err != nil {
  				t.Errorf("Union: r=%s, s=%s, a=%s, r not in a: %v", r, s, a, err)
  			}
  			if err := in(s, a); err != nil {
  				t.Errorf("Union: r=%s, s=%s, a=%s, s not in a: %v", r, s, a, err)
  			}
  			if a.Empty() {
  				// You can't get any smaller than a.
  				continue
  			}
  			smallerThanA := [4]Rectangle{a, a, a, a}
  			smallerThanA[0].Min.X++
  			smallerThanA[1].Min.Y++
  			smallerThanA[2].Max.X--
  			smallerThanA[3].Max.Y--
  			for i, b := range smallerThanA {
  				if in(r, b) == nil && in(s, b) == nil {
  					t.Errorf("Union: r=%s, s=%s, a=%s, b=%s, i=%d: union could be smaller",
  						r, s, a, b, i)
  				}
  			}
  		}
  	}
  }
  

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