How do I animate in/out a gaussian blur effect in iOS?

Question

For the whole iOS 7 feel, I want to apply a blur effect to a specific portion of the screen to obfuscate it, but I don\'t want to just throw the blur on instantly, I want to

Answer 1

I've developed a small project that uses GPUImage for live blurring with variable blur radius and framerate (MSLiveBlur) - this sounds like exactly what you need.

In the sample app I have a slider that increases / decreases the blur level in response to user action, as you mentioned in your question. If you wanted to animate it without user interaction, you could make a timer that slowly increases the blur radius until you reach the final value. You wouldn't be able to use CoreAnimation with this solution though.

[[MSLiveBlurView sharedInstance] setBlurInterval:0.2];
[[MSLiveBlurView sharedInstance] blurRect:someView.frame];

// Count x from 0 to your final radius
[MSLiveBlurView sharedInstance].blurRadius = x;