Sutherland-Hodgman polygon clipping: Difference between revisions

=={{header|Swift}}==

{{trans|Rust}}

<lang swift>struct Point {

var x: Double

var y: Double

}

struct Polygon {

var points: [Point]

init(points: [Point]) {

self.points = points

}

init(points: [(Double, Double)]) {

self.init(points: points.map({ Point(x: $0.0, y: $0.1) }))

}

}

func isInside(_ p1: Point, _ p2: Point, _ p3: Point) -> Bool {

(p3.x - p2.x) * (p1.y - p2.y) > (p3.y - p2.y) * (p1.x - p2.x)

}

func computeIntersection(_ p1: Point, _ p2: Point, _ s: Point, _ e: Point) -> Point {

let dc = Point(x: p1.x - p2.x, y: p1.y - p2.y)

let dp = Point(x: s.x - e.x, y: s.y - e.y)

let n1 = p1.x * p2.y - p1.y * p2.x

let n2 = s.x * e.y - s.y * e.x

let n3 = 1.0 / (dc.x * dp.y - dc.y * dp.x)

return Point(x: (n1 * dp.x - n2 * dc.x) * n3, y: (n1 * dp.y - n2 * dc.y) * n3)

}

func sutherlandHodgmanClip(subjPoly: Polygon, clipPoly: Polygon) -> Polygon {

var ring = subjPoly.points

var p1 = clipPoly.points.last!

for p2 in clipPoly.points {

let input = ring

var s = input.last!

ring = []

for e in input {

if isInside(e, p1, p2) {

if !isInside(s, p1, p2) {

ring.append(computeIntersection(p1, p2, s, e))

}

ring.append(e)

} else if isInside(s, p1, p2) {

ring.append(computeIntersection(p1, p2, s, e))

}

s = e

}

p1 = p2

}

return Polygon(points: ring)

}

let subj = Polygon(points: [

(50.0, 150.0),

(200.0, 50.0),

(350.0, 150.0),

(350.0, 300.0),

(250.0, 300.0),

(200.0, 250.0),

(150.0, 350.0),

(100.0, 250.0),

(100.0, 200.0)

])

let clip = Polygon(points: [

(100.0, 100.0),

(300.0, 100.0),

(300.0, 300.0),

(100.0, 300.0)

])

print(sutherlandHodgmanClip(subjPoly: subj, clipPoly: clip))</lang>

{{out}}

<pre>Polygon(points: [Point(x: 100.0, y: 116.66666666666667), Point(x: 125.00000000000001, y: 100.0), Point(x: 275.0, y: 100.0), Point(x: 300.0, y: 116.66666666666667), Point(x: 300.0, y: 299.99999999999994), Point(x: 250.0, y: 300.0), Point(x: 200.0, y: 250.0), Point(x: 175.0, y: 300.0), Point(x: 125.0, y: 300.0), Point(x: 100.0, y: 250.0)])</pre>