53 Zeilen
1.5 KiB
Go
53 Zeilen
1.5 KiB
Go
package rect
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import (
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"fmt"
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"math"
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)
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// line is described as two Points
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type line struct {
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pt1, pt2 Point
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}
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// determinants aids by calculating necessary values for performing
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// calculations using the determinant of two points
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func determinants(l line) (float64, float64, float64) {
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a := l.pt2.Y - l.pt1.Y
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b := l.pt1.X - l.pt2.X
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c := a*l.pt1.X + b*l.pt1.Y
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return a, b, c
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}
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// lineIntersection returns the Point of intersection between two lines.
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// lineIntersection will only return a point if the point lies on the
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// line, otherwise it will return a nil point and an error
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func lineIntersection(l1, l2 line) (Point, error) {
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a1, b1, c1 := determinants(l1)
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a2, b2, c2 := determinants(l2)
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det := a1*b2 - a2*b1
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if det != 0 {
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x := ((b2*c1 - b1*c2) / det)
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y := ((a1*c2 - a2*c1) / det)
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minx1, maxx1 := math.Min(l1.pt1.X, l1.pt2.X), math.Max(l1.pt1.X, l1.pt2.X)
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miny1, maxy1 := math.Min(l1.pt1.Y, l1.pt2.Y), math.Max(l1.pt1.Y, l1.pt2.Y)
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minx2, maxx2 := math.Min(l2.pt1.X, l2.pt2.X), math.Max(l2.pt1.X, l2.pt2.X)
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miny2, maxy2 := math.Min(l2.pt1.Y, l2.pt2.Y), math.Max(l2.pt1.Y, l2.pt2.Y)
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if minx1 <= x && x <= maxx1 && miny1 <= y && y <= maxy1 {
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if minx2 <= x && x <= maxx2 && miny2 <= y && y <= maxy2 {
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return Point{x, y}, nil
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}
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}
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}
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return Point{}, fmt.Errorf("lines do not intersect")
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}
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// lineOnLine determins if both points of a line, l1, are on the same line, l2
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func lineOnLine(l1, l2 line) bool {
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if onLine(l1.pt1, l1.pt2, l2.pt1) && onLine(l1.pt1, l1.pt2, l2.pt2) {
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return true
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}
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return false
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}
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