图片裁剪 问题
http://www.myexception.cn/android/1674588.html
http://blog.csdn.net/stoppig/article/details/23202129
http://blog.csdn.net/lcore/article/details/8927748
http://www.xycoding.com/articles/2014/11/21/android-clipimage/ (好)
http://stackoverflow.com/questions/3846338/how-to-crop-an-image-in-android