How to add blur and vibrancy using UIVisualEffectView

Swift version: 5.4

Paul Hudson @twostraws May 28th 2019

As of iOS 8.0, visual effects such as blur and vibrancy are a cinch because Apple provides a built in UIView subclass that does all the hard work: UIVisualEffectView. For example, if you want to blur an image, you would use this code:

let imageView = UIImageView(image: UIImage(named: "example"))
imageView.frame = view.bounds
imageView.contentMode = .scaleToFill
view.addSubview(imageView)

let blurEffect = UIBlurEffect(style: .dark)
let blurredEffectView = UIVisualEffectView(effect: blurEffect)
blurredEffectView.frame = imageView.bounds
view.addSubview(blurredEffectView)

As well as blurring content, Apple also lets you add a "vibrancy" effect to your views – this is a translucency effect designed to ensure that text is readable when it's over any kind of blurred background, and it's used to create that soft glow effect you see in the notification center.

We could extend the previous example so that it adds a segmented control in the middle of the view, using a vibrancy effect. This is accomplished by created a second UIVisualEffectView inside the first one, this time using UIVibrancyEffect to create the glow. Note that you need to use the same blur type for both your visual effect views, otherwise the glow effect will be incorrect.

let segmentedControl = UISegmentedControl(items: ["First Item", "Second Item"])
segmentedControl.sizeToFit()
segmentedControl.center = view.center

let vibrancyEffect = UIVibrancyEffect(blurEffect: blurEffect)
let vibrancyEffectView = UIVisualEffectView(effect: vibrancyEffect)
vibrancyEffectView.frame = imageView.bounds

vibrancyEffectView.contentView.addSubview(segmentedControl)
blurredEffectView.contentView.addSubview(vibrancyEffectView)

Warning: you need to add child views to the contentView property of a UIVisualEffectView otherwise they will not be drawn correctly.