Clipper2-swift

A Swift port of Clipper2-java, which itself is a port of the Clipper2 polygon clipping and offsetting library by Angus Johnson.

Clipper2 performs boolean clipping operations (intersection, union, difference, XOR) on both closed polygons and open polylines. It also supports polygon offsetting (inflating/deflating).

Features

• Boolean polygon clipping: intersection, union, difference, XOR
• Polygon offsetting (inflate/deflate) with multiple join types (square, round, miter, bevel)
• Fast rectangular clipping with O(n) performance
• Minkowski sum and difference
• Support for both integer (Int64) and floating-point (Double) coordinates
• PolyTree output for parent-child polygon relationships
• Path simplification (Ramer-Douglas-Peucker)
• Point-in-polygon testing

Requirements

• Swift 5.9+
• iOS 13.0+ / macOS 10.15+

Installation

Swift Package Manager

Add to your Package.swift:

dependencies: [
    .package(url: "https://github.com/zyunlongz/clipper2-swift", from: "1.0.0")
]

Then add "Clipper2" as a dependency of your target:

.target(name: "YourTarget", dependencies: ["Clipper2"])

CocoaPods

pod 'Clipper2-swift'

Usage

Boolean Operations

import Clipper2

// Create subject and clip polygons
let subject: Paths64 = [[
    Point64(0, 0), Point64(100, 0),
    Point64(100, 100), Point64(0, 100)
]]
let clip: Paths64 = [[
    Point64(50, 50), Point64(150, 50),
    Point64(150, 150), Point64(50, 150)
]]

// Intersection
let intersection = Clipper.intersect(subject, clip, .evenOdd)

// Union
let union = Clipper.union(subject, clip, .evenOdd)

// Difference
let difference = Clipper.difference(subject, clip, .evenOdd)

// XOR
let xor = Clipper.xor(subject, clip, .evenOdd)

Polygon Offsetting

let paths: Paths64 = [[
    Point64(0, 0), Point64(100, 0),
    Point64(100, 100), Point64(0, 100)
]]

// Inflate by 10 units with round joins
let inflated = Clipper.inflatePaths(paths, 10, .round, .polygon)

// Deflate by 5 units with miter joins
let deflated = Clipper.inflatePaths(paths, -5, .miter, .polygon)

Rectangle Clipping

let rect = Rect64(100, 100, 300, 300)
let paths: Paths64 = [[
    Point64(0, 0), Point64(200, 0),
    Point64(200, 200), Point64(0, 200)
]]

let clipped = Clipper.rectClip(rect, paths)

Using the Engine Directly

let clipper = Clipper64()
clipper.addSubject(subjectPaths)
clipper.addClip(clipPaths)

var solution: Paths64 = []
clipper.execute(.intersection, .evenOdd, &solution)

Floating-Point Coordinates

let clipperD = ClipperD(roundingDecimalPrecision: 2)
clipperD.addSubject(subjectPathD)
clipperD.addClip(clipPathD)

var solution: PathsD = []
clipperD.execute(.union, .nonZero, &solution)

API Reference

The main entry point is the Clipper enum, which provides static convenience methods for common operations. For more control, use Clipper64 (integer coordinates) or ClipperD (floating-point coordinates) directly.

Key Types

Type	Description
Point64	Integer coordinate point (Int64 x, y)
PointD	Floating-point coordinate point (Double x, y)
Path64	Array of Point64 ([Point64])
PathD	Array of PointD ([PointD])
Paths64	Array of Path64 ([Path64])
PathsD	Array of PathD ([PathD])
Rect64	Integer rectangle (left, top, right, bottom)
ClipType	Boolean operation: .intersection, .union, .difference, .xor
FillRule	Winding rule: .evenOdd, .nonZero, .positive, .negative
JoinType	Offset join: .square, .round, .miter, .bevel
EndType	Offset end: .polygon, .joined, .butt, .square, .round

License

Boost Software License - Version 1.0

Acknowledgments

• Clipper2 by Angus Johnson - the original C# library
• Clipper2-java by Michael Carleton - the Java port this project is based on