RectangleContour

My main product is a library named RectangleContour which contains one Swift module also named RectangleContour. The library implements an algorithm for finding the union of a set of axis-aligned rectangles.

Using the library, you can create shapes like these:

Adding RectangleContour as a Dependency

To use the RectangleContour library as a dependency in a SwiftPM project, add the following to your Package dependencies in your Package.swift manifest:

.package(url: "https://github.com/mayoff/RectangleContour", from: "0.0.2"),

and include "RectangleContour" as a dependency of your Target:

.target(name: "YourExistingTarget", dependencies: [
    .product(name: "RectangleContour", package: "RectangleContour"),
]),

Demo Apps

To run the demo apps, clone the RectangleContour repo and open its RectangleContour.xcworkspace in Xcode. Select the MacDemoApp scheme and the “My Mac” destination, or select the PhoneDemoApp scheme and an iPhone simulator (or real iPhone) destination. Then click Product > Run.

Using the RectangleContour API

For examples of how to use the module, look for the calls to contour and cgPath in RectDemoView.swift, TextDemoView.swift (macOS), and TextDemoView.swift (iOS).

To use the module, you must first prepare a Collection of CGRects. Typically you'll create an array, but you can use any Collection type.

let rects: [CGRect] = [
    CGRect(x: 100, y: 200, width: 300, height: 400),
    CGRect(x: 200, y: 300, width: 500, height: 600),
]

Next, ask the collection for its contour:

let contour: IsoOrientedContour = rects.contour()

Then you'll probably want to convert the contour to a CGPath. The IsoOrientedContour type provides two convenience methods for converting a contour to a CGPath. One creates sharp corners:

let sharpPath: CGPath = contour.cgPath()

The other creates rounded corners:

let roundedPath: CGPath = contour.cgPath(cornerRadius: 10)

If you need a SwiftUI.Path or an UIBezierPath, you can wrap the CGPath:

let swiftuiPath = Path(roundedPath)
let uiPath = UIBezierPath(cgPath: roundedPath)

Implementation Notes

This package implements the algorithm described in the 1979 paper “Finding the Contour of a Union of Iso-Oriented Rectangles” by Witold Lipski Jr. and Franco P. Preparata.