滚筒图片效果

http://www.code4app.com/ios/3D-UICollectionView/53042b07cb7e84d34c8b557a

http://code4app.com/ios/53042b07cb7e84d34c8b557a

https://www.jianshu.com/p/4da6d8a30d04

http://download.jikexueyuan.com/detail/id/71.html

https://www.jianshu.com/p/4da6d8a30d04

http://www.internetke.com/effects/focus/2014/1214/1012.html