博客园 http://www.cnblogs.com/v2m_/archive/2013/05/09/3070187.html 知乎 ： http://segmentfault.com/q/1010000000134502            1: 苹果官方文档：       https://developer.apple.com/library/ios/document

CoreGraphics.h CGAffineTransform rotation = CGAffineTransformMakeRotation(M_PI_2);
[xxx setTransform:rotation];
呵呵就这么简单的两行代码就可以实现了！ 顺便记录一些常量，以后用的着！ #define M_E         2.71828182845904523536028747135

1. CGAffineTransform 仿射变换   1.1 移动   _imageView.transform = CGAffineTransformMakeTranslation(100, 100);   1.2 缩放 _imageView.transform = CGAffineTransformMakeScale(2, 2);  1.3  累计方法缩小 n