Blur Image On Launch of App

Question

I'm trying to write an iPhone app that, when launched, a launch image appears and then takes 2.5 seconds to blur. Once the blur effect is complete, that is when I want the rest of the UI to appear.

I was going to use the following code to blur the image:

[UIView transitionWithView:self.view duration:2.5 options:UIViewAnimationOptionTransitionCrossDissolve animations:^{
    self.backgroundImage.image = [UIImage imageNamed:@"640 x 960 Blur10_iOS7@2x.png"];
} completion:^(BOOL finished) {

}];

BackgoundImage is initialized with the regular view of the image and it takes 2.5 seconds to transition to the blur10 view of the image. However, when I run this code from the didViewLoad method, the application opens with the already blurred view of the image and doesn't show the animation. If I run the code from a button press, it works perfectly.

Answer 1

You should put it in:

- (void) viewDidAppear:(BOOL)animated {
    // put stuff here
}

That way, it won't run until the view is visible.

Or, you could prep it in viewWillAppear and start the fade in viewDidAppear.

- (void) viewWillAppear:(BOOL)animated {
    // view is about to appear, set up your blur
} 

- (void) viewDidAppear:(BOOL)animated {
    // view has appeared, start your blur.
}

Answer 2

Blurring an image is an expensive operation. Making an animation that blurs over time is even more expensive and probably won't run as you expect.

You'd be better of creating a number of different images all with different amounts of blur and then animating them in a UIImageView using animationImages and startAnimating.