title: Sharing an Image between two viewControllers during a transition animation
body: <p>I have came across really cool transitions between viewControllers since UIViewControllerAnimatedTransitioning protocol was made available in IOS 7. Recently I noticed a particularly interesting one in Intacart's IOS app. </p>
  
  <p>Here is the animation I am talking about in slow motion: 
  <a href="https://www.dropbox.com/s/p2hxj45ycq18i3l/Video%20Oct%2015%2C%207%2023%2059%20PM.mov?dl=0" rel="noreferrer">https://www.dropbox.com/s/p2hxj45ycq18i3l/Video%20Oct%2015%2C%207%2023%2059%20PM.mov?dl=0</a></p>
  
  <p>First I thought it was similar to what the author walks through in this tutorial, with some extra fade-in and fade-out animations: <a href="http://www.raywenderlich.com/113845/ios-animation-tutorial-custom-view-controller-presentation-transitions" rel="noreferrer">http://www.raywenderlich.com/113845/ios-animation-tutorial-custom-view-controller-presentation-transitions</a></p>
  
  <p>But then if you look at it closely, it seems like the product image transitions between the two viewControllers as the first viewController fades out. The reason why I think there are two viewControllers is because when you swipe the new view down, you can still see the original view behind it with no layout changes. </p>
  
  <p>Maybe two viewControllers actually have the product image (not faded out) and are somehow animating at the same time with perfect precision and one of them fades in as the other fades out. </p>
  
  <p>What do you think is actually going on there? </p>
  
  <p>How is it possible to program such a transition animation that it looks like an image is shared between two viewControllers? </p>