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add more polygon tests (also they pass now)

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This commit is contained in:
Josh Deprez 2021-09-08 20:22:18 +10:00
parent b08cb774e1
commit b2e2a370fc
2 changed files with 43 additions and 8 deletions
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10
geom/polygon.go
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@ -4,11 +4,11 @@ import "image"
// PolygonContains reports if a polygon contains a point
func PolygonContains(polygon []image.Point, p image.Point) bool {
for i, p1 := range polygon {
p2 := polygon[(i+1)%len(polygon)]
// ∆(p p1 p2) should have positive signed area
p1, p2 = p1.Sub(p), p2.Sub(p)
if p2.X*p1.Y-p1.X*p2.Y < 0 {
for i, q := range polygon {
r := polygon[(i+1)%len(polygon)]
// ∆(p q r) should have positive signed area
q, r = q.Sub(p), r.Sub(p)
if q.X*r.Y > r.X*q.Y {
return false
}
}

41
geom/polygon_test.go
View file

@ -8,21 +8,56 @@ import (
func TestPolygonContains(t *testing.T) {
square5 := []image.Point{
{X: 0, Y: 0},
{X: 5, Y: 0},
{X: 5, Y: 5},
{X: 0, Y: 5},
{X: 5, Y: 5},
{X: 5, Y: 0},
}
pentagon := []image.Point{
{X: -5, Y: -4},
{X: -7, Y: 2},
{X: 0, Y: 7},
{X: 7, Y: 2},
{X: 5, Y: -4},
}
hexagon := []image.Point{
{X: 8, Y: 0},
{X: 0, Y: 8},
{X: 8, Y: 16},
{X: 23, Y: 16},
{X: 31, Y: 8},
{X: 23, Y: 0},
}
tests := []struct {
polygon []image.Point
point image.Point
want bool
}{
{square5, image.Pt(2, 3), true},
{square5, image.Pt(0, 0), true},
{square5, image.Pt(5, 5), true},
{square5, image.Pt(-5, 0), false},
{square5, image.Pt(0, -5), false},
{square5, image.Pt(6, 6), false},
{pentagon, image.Pt(0, 0), true},
{pentagon, image.Pt(8, 0), false},
{pentagon, image.Pt(1, 1), true},
{pentagon, image.Pt(-1, -1), true},
{pentagon, image.Pt(-10000, 10000), false},
{hexagon, image.Pt(0, 0), false},
{hexagon, image.Pt(16, 8), true},
{hexagon, image.Pt(0, 8), true},
{hexagon, image.Pt(-1, 8), false},
{hexagon, image.Pt(31, 8), true},
{hexagon, image.Pt(32, 8), false},
{hexagon, image.Pt(10000, 10000), false},
}
for _, test := range tests {
if got, want := PolygonContains(test.polygon, test.point), test.want; got != want {
t.Errorf("polygonContains(%v, %v) = %v, want %v", test.polygon, test.point, got, want)
t.Errorf("PolygonContains(%v, %v) = %v, want %v", test.polygon, test.point, got, want)
}
}
}