UIPinchGestureRecognizer

http://stackoverflow.com/questions/5647084/limit-maximum-scale-for-scaling-image-with-pinch-gesture-in-ios

 

http://stackoverflow.com/questions/3406179/uipinchgesturerecognizer-zoom-out-zoom-in

 

http://stackoverflow.com/questions/4947148/uipinchgesturerecognizer-position-the-pinched-view-between-the-two-fingers

 

 

http://developer.apple.com/library/ios/#documentation/EventHandling/Conceptual/EventHandlingiPhoneOS/GestureRecognizers/GestureRecognizers.html

 

http://blog.sina.com.cn/s/blog_45e2b66c0100zwu8.html  //截圖

 

http://iphonedevelopertips.com/cocoa/how-to-mask-an-image.html