How to draw color gradients using CAGradientLayer

Swift version: 5.10

Paul Hudson @twostraws May 28th 2019

I love CAGradientLayer because it takes just four lines of code to use, and yet looks great because it quickly and accurately draws smooth color gradients use Core Graphics. Here's a basic example:

let layer = CAGradientLayer()
layer.frame = CGRect(x: 64, y: 64, width: 160, height: 160)
layer.colors = [UIColor.red.cgColor, UIColor.black.cgColor]
view.layer.addSublayer(layer)

Note that you need to fill in an array of colors that will be used to draw the gradient. You can provide more than one if you want to, at which point you will also need to fill in the locations array to tell CAGradientLayer where each color starts and stops. Note that you need to specify your colors as CGColor and not UIColor.

If you want to make your gradient work in a different direction, you should set the startPoint and endPoint properties. These are both CGPoints where the X and Y values are between 0 and 1, where 0 is one edge and 1 is the opposite edge. The default start point is X 0.5, Y 0.0 and the default end point is X 0.5, Y 1.0, which means both points are in the center of the layer, but it starts at the top and ends at the bottom.

You might be interested to know that CAGradientLayer happily works with translucent colors, meaning that you can make a gradient that fades out.