参考：
http://www.cocoachina.com/ios/20140812/9363.html
http://www.cocoachina.com/ios/20140925/9756.html
GPUImage资料github:
https://github.com/BradLarson/GPUImage
iOS中图像处理技术资料：
原文：http://www.cnblogs.com/canghaixiaoyuer/p/4713023.html
