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A UIView category to blur a view.


UIView+Blur can be installed by copying the files inside the UIViewBlur directory.

There is also a UIViewBlur.podspec podspec file you can easily add UIView+Blur to your project adding this line to your Podfile:

pod "UIViewBlur", :podspec => ""

We will soon fully support Cocoapods to provide an even easier method to integrate it in your project.

Getting started

After integrating UIView+Blur into your project, a new blur property is available for all UIViews.

@property (nonatomic, assign) float blur;

IMPORTANT Whenever the property is set for the first time, snapshots of the UIView backing layer will be created, therefore be careful memory and CPU-wise it's quite an intensive operation.

Snapshots are created the first time blur property is set.


You can access the blurredLayer property of the UIView and set the blur value directly. You can also animate the value with explicit CoreAnimation animations.

// adds the blurred layer to the image, creates snapshots
self.imageView.blur = 0;

CABasicAnimation *animation = [CABasicAnimation animationWithKeyPath:@"blur"];
[animation setFromValue:@(0.0)];
[animation setToValue:@(1.0)];
[animation setDuration:2.0f];
[self.imageView.blurredLayer addAnimation:animation forKey:@"blur"];

self.imageView.blurredLayer.blur = 1;

Technical details

The library has been written using ARC. It can still be used on non-ARC projects by enabling the -fobj-arc compiler flag on the .m files.

The library was tested on iOS 7 only, but it should work on previous iOS versions as well.

Fine tuning

There are some macros defined in UIView+Blur.m

#define maxBlurRadius 20.0f

defines the maximum blur radius used (ranges between 0 to maxBlurRadius).

#define steps 20

number of images stored, the higher the number the slower the -updateSnapshots method takes.

#define asyncBlur YES

on -updateSnapshots setting this macro to NO blurs the snapshot on the main thread, blocking the UI.

IMPORTANT By setting it to YES, the snapshot will be blurred in the background with low priority but it may delay to show the blurred effect.

Implicit animations

CoreAnimation explicit animations work by setting the blur property on the blurredLayer as stated above.

UIView animations (e.g. [UIView animateWithDuration:..]) do not work, there are hacks (method swizzling) to make them work, but I would stick to CoreAnimation.

You can enable implicit animations by setting the relative macro

#define implicitAnimationsDisabled YES

This will actually make -actionForKey: on the CABlurLayer return an animation.

To animate then just set the blur property on the UIView blurredLayer

self.imageView.blur = 0; // creates the blurredLayer (needed just the first time!)
self.imageView.blurredLayer.blur = 1;

Refer to the demo porject UIViewBlurDemo for a concrete example on how to use the category.

Considerations & Donations

I started this project after seeing background image blurred when dragging a scrollview.

This is an open-source project built during my spare time, feel free to contribute to the project. I got to learn something more about CoreAnimation, so I hope you appreciate the effort ;)

If you want to get some specific features implemented first or you need help to set it up in your own project, get in touch.

To speed-up development donations are very welcome.


Category on UIView to blur the view through a property (animatable).