其实你只需要的是圆角图片。。。。。
UIGraphicsBeginImageContextWithOptions(image.size, NO, image.scale);
[[UIBezierPath bezierPathWithRoundedRect:RECT cornerRadius:RADIUS] addClip];
[image drawInRect:RECT];
UIImage* imageNew = UIGraphicsGetImageFromCurrentImageContext();
UIGraphicsEndImageContext();原文：http://www.cnblogs.com/starainDou/p/5246375.html