There is an animation to increase the picture, and how to do the opposite decrease
UIView.animateWithDuration(transitionDuration(transitionContext), animations: { snapshotView.transform = CGAffineTransformMakeScale(1.5, 1.5); }, completion: { finished -> Void in snapshotView.transform = CGAffineTransformMakeScale(1.0, 1.0) })