Computing the union 2 MKPolygons
I am working on map applications with polygon MKOverlays. I have a requirement to merge (union) overlapping polygons.
Is there a well known algorithm to do this? Are there any free existing libraries/implementations that help with such geometry operations?
I have found the GEOS开发者_高级运维 library, but apparently its licensing terms disallow use without distributing your source code. Is anyone else using this library. If yes, where can I find the way to include this in my Xcode project.
The only free libraries I'm aware of are -
Clipper: http://angusj.com/delphi/clipper.php
Boost Polygon: http://www.boost.org/doc/libs/1_47_0/libs/polygon/doc/index.htm
Boost Geometry: http://trac.osgeo.org/ggl/
Try gpc. They have several licences. Also there are similar libraries listed on their page.
There is a great library RSClipperWrapper which is basically a wrapper for Clipper. There is even a great library comparison inside their website:
TL;DR, free library, error free and fast.
A few notes:
- RSClipperWrapper takes
CGPoint
but fear not, you can pass lat/long into it and it will get the job done (tested and verified). For convinice I've written an extension so we can just pass a custom
Polygon
array and get the merged polygons - if you're usingMKPolygon
or other type then don't forget adjust your type:extension Clipper { static func union(polygons: [Polygon]) -> [Polygon] { let pointsPolygons = convert(polygons: polygons) let unionfied = Clipper.unionPolygons(pointsPolygons, withPolygons: pointsPolygons) return convert(pointsPolygons: unionfied) } static func convert(polygons: [Polygon]) -> [[CGPoint]] { var polygonsPoints: [[CGPoint]] = [] for polygon in polygons { var points: [CGPoint] = [] for location in polygon.locations { points.append(CGPoint(x: location.coordinate.latitude, y: location.coordinate.longitude)) } polygonsPoints.append(points) } return polygonsPoints } static func convert(pointsPolygons: [[CGPoint]]) -> [Polygon] { var polygons: [Polygon] = [] for pointsPolygon in pointsPolygons { var locations: [CLLocation] = [] for point in pointsPolygon { locations.append(CLLocation(latitude: CLLocationDegrees(point.x), longitude: CLLocationDegrees(point.y))) } let polygon = Polygon(locations: locations) polygons.append(polygon) } return polygons } }
精彩评论