https://github.com/calda/cgpathintersection

:curly_loop: A library that identifies points where two CGPaths intersect
https://github.com/calda/cgpathintersection

core-graphics intersection ios swift

Last synced: 3 months ago
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:curly_loop: A library that identifies points where two CGPaths intersect

• Host: GitHub
• URL: https://github.com/calda/cgpathintersection
• Owner: calda
• License: mit
• Created: 2016-11-13T18:52:51.000Z (about 8 years ago)
• Default Branch: master
• Last Pushed: 2022-02-05T23:54:57.000Z (about 3 years ago)
• Last Synced: 2024-10-14T03:42:35.350Z (4 months ago)
• Topics: core-graphics, intersection, ios, swift
• Language: Swift
• Homepage:
• Size: 6.2 MB
• Stars: 69
• Watchers: 5
• Forks: 5
• Open Issues: 0
• Metadata Files:
  • Readme: README.md
  • License: LICENSE

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README

        
# CGPathIntersection

[![](https://img.shields.io/endpoint?url=https%3A%2F%2Fswiftpackageindex.com%2Fapi%2Fpackages%2Fcalda%2FCGPathIntersection%2Fbadge%3Ftype%3Dswift-versions)](https://swiftpackageindex.com/calda/CGPathIntersection) [![](https://img.shields.io/endpoint?url=https%3A%2F%2Fswiftpackageindex.com%2Fapi%2Fpackages%2Fcalda%2FCGPathIntersection%2Fbadge%3Ftype%3Dplatforms)](https://swiftpackageindex.com/calda/CGPathIntersection)

**CGPathIntersection** is a library for iOS, macOS, and tvOS that identifies points where two `CGPath`s intersect.

Surprisingly, this is not provided out-of-the-box by `CoreGraphics`. Intersections can be calculated analytically for simple geometric shapes (especially straight lines), but that method becomes rather challenging when considering a `CGPath` can be arbitrarily complex. `CGPathIntersection` solves this problem by rendering each path into an image and then finding the exact pixels where they intersect.

## Installation

#### [Swift Package Manager](https://www.swift.org/package-manager/)

Add the following dependency to your package definition:

```swift

.package(

  name: "CGPathIntersection",

  url: "https://github.com/calda/CGPathIntersection.git",

  from: "4.0.0")

```

#### [Carthage](https://github.com/Carthage/Carthage)

Add `github "calda/CGPathIntersection"` to your Cartfile

#### [CocoaPods](https://github.com/cocoapods/cocoapods)

Add `pod 'CGPathIntersection'` to your Podfile

## Usage

```swift

import CGPathIntersection

let path1 = CGPath(...)

let path2 = CGPath(...)

        

path1.intersects(path2) // returns a boolean

path1.intersectionPoints(with: path2) // returns an array of points

```

If performing many calculations, you can increase performance by creating a `CGPathImage`. Any calculations performed on a pre-existing `CGPathImage` will run faster than the same calculation performed on a raw `CGPath`.

```swift

import CGPathIntersection

let pathImage = CGPathImage(from: CGPath(...))

let otherPathImages: [CGPathImage] = [...]

let intersectingPaths = otherPathImages.filter { pathImage.intersects($0) }

```

## Example

CGPathIntersection was created as a component of **[Streets](http://github.com/calda/Streets)**, a prototype SpriteKit game that simulates managing a network of streets. Streets uses CGPathIntersection to connect individual roads together with physical intersections. When a car reaches an intersection, it makes a random turn onto one of the other connected roads.



     



Streets also has some support for more complex paths, like roundabouts: