iphone 截屏保存

UIGraphicsBeginImageContext(self.view.bounds.size);
//UIGraphicsBeginImageContextWithOptions(self.view.bounds.size, NO, 0.0);
[self.view.layer renderInContext:UIGraphicsGetCurrentContext()];
UIImage *viewImage = UIGraphicsGetImageFromCurrentImageContext();
UIGraphicsEndImageContext();
UIImageWriteToSavedPhotosAlbum(viewImage, self, nil, nil);