[英]MKPolygon - How to determine if a CLLocationCoordinate2D is in a CLLocationCoordinate2D polygon?
I have the swift code below that draws a polygon and drops an annotation on MKMapView.我有下面的 swift 代码,它绘制一个多边形并在 MKMapView 上放置一个注释。 I am trying to figure out how i could identify if the annotation's coordinate is within the polygon?我想弄清楚如何识别注释的坐标是否在多边形内?
import UIKit
import MapKit
class ViewController: UIViewController {
@IBOutlet weak var mapView: MKMapView!
override func viewDidLoad() {
super.viewDidLoad()
let initialLocation = CLLocation(latitude: 49.140838, longitude: -123.127886)
centerMapOnLocation(initialLocation)
addBoundry()
var annotation = MKPointAnnotation()
annotation.coordinate = point1
annotation.title = "Roatan"
annotation.subtitle = "Honduras"
mapView.addAnnotation(annotation)
}
var points = [CLLocationCoordinate2DMake(49.142677, -123.135139),
CLLocationCoordinate2DMake(49.142730, -123.125794),
CLLocationCoordinate2DMake(49.140874, -123.125805),
CLLocationCoordinate2DMake(49.140885, -123.135214)]
var point1 = CLLocationCoordinate2DMake(49.141821, -123.131577)
func addBoundry() {
let polygon = MKPolygon(coordinates: &points, count: points.count)
mapView.addOverlay(polygon)
}
let regionRadius: CLLocationDistance = 1000
func centerMapOnLocation(location: CLLocation) {
let coordinateRegion = MKCoordinateRegionMakeWithDistance(location.coordinate, regionRadius * 2.0, regionRadius * 2.0)
mapView.setRegion(coordinateRegion, animated: true)
}
func mapView(mapView: MKMapView!, rendererForOverlay overlay: MKOverlay!) -> MKOverlayRenderer! {
if overlay is MKPolygon {
let polygonView = MKPolygonRenderer(overlay: overlay)
polygonView.strokeColor = UIColor.magentaColor()
return polygonView
}
return nil
}
}
I created a Swift version of the answer by @StefanS and made it easier to read by porting the code from this answer我创建了@StefanS 答案的 Swift 版本,并通过移植此答案中的代码使其更易于阅读
func isPoint(point: MKMapPoint, insidePolygon poly: MKPolygon) -> Bool {
let polygonVerticies = poly.points()
var isInsidePolygon = false
for i in 0..<poly.pointCount {
let vertex = polygonVerticies[i]
let nextVertex = polygonVerticies[(i + 1) % poly.pointCount]
// The vertices of the edge we are checking.
let xp0 = vertex.x
let yp0 = vertex.y
let xp1 = nextVertex.x
let yp1 = nextVertex.y
if ((yp0 <= point.y) && (yp1 > point.y) || (yp1 <= point.y) && (yp0 > point.y))
{
// If so, get the point where it crosses that line. This is a simple solution
// to a linear equation. Note that we can't get a division by zero here -
// if yp1 == yp0 then the above if be false.
let cross = (xp1 - xp0) * (point.y - yp0) / (yp1 - yp0) + xp0
// Finally check if it crosses to the left of our test point. You could equally
// do right and it should give the same result.
if cross < point.x {
isInsidePolygon = !isInsidePolygon
}
}
}
return isInsidePolygon
}
- (BOOL)isPoint:(MKMapPoint)point insidePolygon:(MKPolygon *)poly {
MKMapPoint *a = poly.points;
BOOL isInsidePolygon = NO;
double testx = point.x;
double testy = point.y;
NSUInteger i = 0, j = 0, nvert = [poly pointCount];
for (i = 0, j = nvert - 1; i < nvert; j = i++) {
if (((a[i].y >= testy) != (a[j].y >= testy)) &&
(testx <= (a[j].x - a[i].x) * (testy - a[i].y) / (a[j].y - a[i].y) + a[i].x)) {
isInsidePolygon = !isInsidePolygon;
}
}
return isInsidePolygon;
}
Because the points xy are in Mercator projection coordinates, this makes sense and you don't need to convert to spherical coordinates for the calculation.因为点 xy 在墨卡托投影坐标中,这是有道理的,您不需要转换为球坐标进行计算。
Why this is a correct calculation here .为什么这是一个正确的计算在这里。
EDIT: updated so that the calculation also considers a point on the line as inside the poly.编辑:更新以便计算也将线上的一个点视为多边形内部。
How about using MkPolygon.intersect()?使用 MkPolygon.intersect() 怎么样? This requires converting the point to a tiny MKMapRect, but it is simpler and may get some acceleration from the underlying API:这需要将点转换为一个很小的 MKMapRect,但它更简单,并且可以从底层 API 获得一些加速:
func pointIsInside(point: MKMapPoint, polygon: MKPolygon) -> Bool {
let mapRect = MKMapRectMake(point.x, point.y, 0.0001, 0.0001)
return polygon.intersects(mapRect)
}
You can create a polygon renderer object and check if it's path contains the point based on the location in the map:您可以创建一个多边形渲染器对象,并根据地图中的位置检查它的路径是否包含该点:
func checkIf(_ location: CLLocationCoordinate2D, areInside polygon: MKPolygon) -> Bool {
let polygonRenderer = MKPolygonRenderer(polygon: polygon)
let mapPoint = MKMapPointForCoordinate(location)
let polygonPoint = polygonRenderer.point(for: mapPoint)
return polygonRenderer.path.contains(polygonPoint)
}
Method to be attached to a gesture recognizer:附加到手势识别器的方法:
@objc
func mapTapped(_ tap: UILongPressGestureRecognizer) {
if tap.state == .recognized {
let touchPoint = tap.location(in: mapView)
let coord = mapView.convert(touchPoint, toCoordinateFrom: mapView)
for overlay: MKOverlay in mapView.overlays {
if let polygon = overlay as? MKPolygon {
let renderer = MKPolygonRenderer(polygon: polygon)
let mapPoint = MKMapPoint(coord)
let rendererPoint = renderer.point(for: mapPoint)
if renderer.path.contains(rendererPoint) {
// here comes your code
}
}
}
}
}
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