Written by 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
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