如何生成圆形的图片

self.headImageView = [[UIImageView alloc]initWithFrame:CGRectMake(124, 40, 72, 72)];
self.headImageView.layer.borderWidth = 2.0;//边宽
self.headImageView.layer.borderColor = [UIColor colorWithWhite:1.0 alpha:0.3].CGColor;//边颜色
self.headImageView.layer.cornerRadius = 36;//切圆角视图，为高的一半
self.headImageView.layer.masksToBounds = YES;//切割多余视图
self.headImageView.image = [UIImage imageNamed:@"add_photo_hav"];//默认图片 
[self.view addSubview:self.headImageView];

1 - (void)imagePickerController:(UIImagePickerController *)picker didFinishPickingMediaWithInfo:(NSDictionary *)info{
2     UIImage *image = [info objectForKey:@"UIImagePickerControllerEditedImage"];
3     image = [Photo scaleImage:image toWidth:100 toHeight:100];//切的图片要比视图大
4     self.headImageView.image = image;
5     [self dismissViewControllerAnimated:YES completion:nil];    
6 }