NEW! Master Swift design patterns with my latest book! >>

How to draw a circle using Core Graphics: addEllipse(in:)

Paul Hudson       @twostraws

Core Graphics is able to draw circles and ellipses with just a few lines of code, although there is some set up to do first. The example code below creates a 512x512 circle with a red fill and a black border:

let renderer = UIGraphicsImageRenderer(size: CGSize(width: 512, height: 512))
let img = renderer.image { ctx in
    ctx.cgContext.setFillColor(UIColor.red.cgColor)
    ctx.cgContext.setStrokeColor(UIColor.green.cgColor)
    ctx.cgContext.setLineWidth(10)

    let rectangle = CGRect(x: 0, y: 0, width: 512, height: 512)
    ctx.cgContext.addEllipse(in: rectangle)
    ctx.cgContext.drawPath(using: .fillStroke)
}

Please note: although a 10-point border is specified, Core Graphics draws borders half-way inside and half-way outside the path you create, so if you want to see the whole border (rather than have it cropped) you either need to draw a smaller shape or create a bigger context.

Available from iOS 4.0 – see Hacking with Swift tutorial 27

Did this solution work for you? Please pass it on!

Other people are reading…

About the Swift Knowledge Base

This is part of the Swift Knowledge Base, a free, searchable collection of solutions for common iOS questions.

Upgrade to premium

The Hacking with Swift guide book helps you learn faster, plus get an Xcode tips and tricks video and Swift wall chart.

MASTER SWIFT NOW
Buy Practical iOS 12 Buy Pro Swift Buy Swift Design Patterns Buy Practical iOS 11 Buy Swift Coding Challenges Buy Server-Side Swift (Vapor Edition) Buy Server-Side Swift (Kitura Edition) Buy Hacking with macOS Buy Advanced iOS Volume One Buy Hacking with watchOS Buy Hacking with tvOS Buy Hacking with Swift Buy Dive Into SpriteKit Buy Swift in Sixty Seconds Buy Objective-C for Swift Developers Buy Beyond Code

Was this page useful? Let me know!

Average rating: 5.0/5

Click here to visit the Hacking with Swift store >>