Images

Links

• CGContextDrawImage Function Reference
• AVMakeRect Function Reference

Drawing an Image the Easy Way

If you can use UIKit and don't need a ton of customization, you can draw like this:

let image = #imageLiteral(resourceName: "Yosemite@2x.png")
image.draw(in: bounds)

This will draw the image in the current context.

Drawing the Hard Way

With Core Graphics you have more control over how the drawing happens. We’ll make use of a little-known function from AVFoundation called AVMakeRect. With this you can skip the aspect ratio math to make sure that you draw an image without stretching.

context.saveGState()

context.translateBy(x: bounds.midX, y: bounds.midY)
context.scaleBy(x: 1, y: -1)
context.translateBy(x: -bounds.midX, y: -bounds.midY)

let rect = AVMakeRect(aspectRatio: image.size, insideRect: bounds)
context.draw(image.cgImage!, in: rect)

context.setBlendMode(.overlay)

context.draw(#imageLiteral(resourceName: "Underwater@2x.png").cgImage!, in: bounds)

context.restoreGState()

Here we use the blend mode of .overlay, but you should play with the various blending modes and see what they do.