iOS 7 parallax effect in my view controller

Question

I\'m developing an app for iOS 7 in Objective-C. I\'ve got a screen in my app with a few buttons and a pretty background image. (It\'s a simple xib with UIButtons

Answer 1

Translated to swift in case anyone is lazy. Please vote @veducm answer up if you found this useful

@IBOutlet var background : UIImageView!

func parallaxEffectOnBackground() {
    let relativeMotionValue = 50
    var verticalMotionEffect : UIInterpolatingMotionEffect = UIInterpolatingMotionEffect(keyPath: "center.y",
        type: .TiltAlongVerticalAxis)
    verticalMotionEffect.minimumRelativeValue = -relativeMotionValue
    verticalMotionEffect.maximumRelativeValue = relativeMotionValue

    var horizontalMotionEffect : UIInterpolatingMotionEffect = UIInterpolatingMotionEffect(keyPath: "center.x",
        type: .TiltAlongHorizontalAxis)
    horizontalMotionEffect.minimumRelativeValue = -relativeMotionValue
    horizontalMotionEffect.maximumRelativeValue = relativeMotionValue

    var group : UIMotionEffectGroup = UIMotionEffectGroup()
    group.motionEffects = [horizontalMotionEffect, verticalMotionEffect]

    self.background.addMotionEffect(group)
}

Answer 2

@veducm's solution can be a little shorter. The UIMotionEffectGroup for its x and y motion is obsolete if you add the the x and y-axis motionEffects separately.

UIInterpolatingMotionEffect *motionEffect;
motionEffect = [[UIInterpolatingMotionEffect alloc] initWithKeyPath:@"center.x"
                                                               type:UIInterpolatingMotionEffectTypeTiltAlongHorizontalAxis];
motionEffect.minimumRelativeValue = @(-25);
motionEffect.maximumRelativeValue = @(25);
[bgView addMotionEffect:motionEffect];

motionEffect = [[UIInterpolatingMotionEffect alloc] initWithKeyPath:@"center.y"
                                                               type:UIInterpolatingMotionEffectTypeTiltAlongVerticalAxis];
motionEffect.minimumRelativeValue = @(-25);
motionEffect.maximumRelativeValue = @(25);
[bgView addMotionEffect:motionEffect];

Answer 3

UIMotionEffect provides a free parallax implementation on iOS 7.

http://www.teehanlax.com/blog/introduction-to-uimotioneffect/

https://github.com/michaeljbishop/NGAParallaxMotion lets you just set the parallax intensity.