Implment iOS system opening app zoom in/out animation effect - ios

Question

If user turn on the iOS 7 or above dynamic effect, when user taps an app icon, the system will have a zoom out/in effect for the app icon and its view, then go to start the app. I want to achieve similar zoom out/in animation. Any good implementations?
I got most code ready, like below, but not the exact animation I want:
#implementation PushAnimator
- (NSTimeInterval)transitionDuration:(id<UIViewControllerContextTransitioning>)transitionContext {
return 0.5;
}
- (void)animateTransition:(id<UIViewControllerContextTransitioning>)transitionContext {
UIViewController* toViewController = [transitionContext viewControllerForKey:UITransitionContextToViewControllerKey];
UIViewController* fromViewController = [transitionContext viewControllerForKey:UITransitionContextFromViewControllerKey];
[[transitionContext containerView] addSubview:toViewController.view];
toViewController.view.alpha = 0;
UIApplication *app = [UIApplication sharedApplication];
MCAppDelegate *appDelegate = (MCAppDelegate *)app.delegate;
// CGRect fromFrame = appDelegate.UserTouchView.frame;
// CGRect toFrame = toViewController.view.frame;
//
CGFloat xFactor = fromViewController.view.frame.size.width / appDelegate.UserTouchView.frame.size.width;
CGFloat yFactor = fromViewController.view.frame.size.height / appDelegate.UserTouchView.frame.size.height;
[UIView animateWithDuration:[self transitionDuration:transitionContext] animations:^{
appDelegate.UserTouchView.transform = CGAffineTransformMakeScale(xFactor,yFactor);
toViewController.view.transform = CGAffineTransformMakeScale(1, 1);
toViewController.view.alpha = 1;
} completion:^(BOOL finished) {
fromViewController.view.transform = CGAffineTransformIdentity;
[transitionContext completeTransition:![transitionContext transitionWasCancelled]];
}];
}
#end