Fix UIVisualEffectView extra light blur being gray on white background

Question

Apple provides this live blurring view class UIVisualEffectView and you use it with a UIBlurEffect which takes one of three available UIBlurEffectStyles:

enum UIBlurEffectStyle : Int {
    case ExtraLight
    case Light
    case Dark
}

Now for demo purposes I set up two effect views with the styles Light and ExtraLight:

let lightBlur = UIBlurEffect(style: UIBlurEffectStyle.Light)
let extraLightBlur = UIBlurEffect(style: UIBlurEffectStyle.ExtraLight)

let lightView = UIVisualEffectView(effect: lightBlur)
lightView.frame = CGRectMake(10, 30, 150, 150)
self.view.addSubview(lightView)

let extraLightView = UIVisualEffectView(effect: extraLightBlur)
extraLightView.frame = CGRectMake(160, 30, 150, 150)
self.view.addSubview(extraLightView)

So far so good, everything works as expected, they blur images:

and kind of work on colors, too:

but when it comes to a white background this happens:

The Light effect on the left works as expected, but the ExtraLight effect on the right leaves some kind of gray square behind.

Now the question: Is there any kind of trick or method that would enable me to use an extra light blur effect on white background (with live blurring support) AND remove that ugly gray shadow?

Answer 1

If you just want the blur and your blurred view is gonna be stationary, you could use the UIImageEffects class and change the tintColor to a "full" white:

- (UIImage *)applyExtraLightEffect
{
    UIColor *tintColor = [UIColor colorWithWhite:0.97 alpha:0.82];
    return [self applyBlurWithRadius:20 tintColor:tintColor saturationDeltaFactor:1.8 maskImage:nil];
}

As far as I know you can't change it in the UIVisualEffectView.

Answer 2

You can try :

var visualEffectView = UIVisualEffectView(effect: UIBlurEffect(style: .Light))    
visualEffectView.frame = imageView.bounds
imageView.addSubview(visualEffectView)

Answer 3

Simple Solution

I could find a simple solution inspired by Shannon Hughes' Blog Post. Just add a white background color with transparency to the effect view. I don't know if it is exactly like extraLight but for me it is close enough.

let visualEffectView = UIVisualEffectView(effect: UIBlurEffect(style: .light))
visualEffectView.frame = sectionHeaderView.bounds
visualEffectView.backgroundColor = UIColor(white: 1.0, alpha: 0.9)
sectionHeaderView.addSubview(visualEffectView)

Answer 4

Works with Swift 5

My way of making the visual effect view completely white when the background view is white.

let blurView = UIVisualEffectView(effect: UIBlurEffect(style: .light))
blurView.backgroundColor = UIColor.white.withAlphaComponent(0.7)

Answer 5

let vc = UIViewController()
vc.view.frame = self.view!.frame
let efv = UIVisualEffectView(effect: UIBlurEffect(style: UIBlurEffectStyle.light))
efv.frame = vc.view.frame
vc.view.addSubview(efv)
self.addChildViewController(vc)
self.view.addSubview(vc.view)
// below method has a bug
// self.present(vc, animated: true, completion:nil)

Answer 6

I would recommend adding your extraLightView to a view of UIColor(white: 1.0, alpha: 0.x), where x can be modified based on the scroll view's contentOffset. When there's nothing behind the view, your extraLightView will be white when x is 1. When you scroll and modify x, you won't be modifying the UIVisualEffectView (which is highly discouraged), but rather its parent view, which is perfectly safe.