将图片转化为圆的

- (void)viewDidLoad {
    [super viewDidLoad];
    // Do any additional setup after loading the view, typically from a nib.
    
    UIImageView *imageView=[[UIImageView alloc] initWithFrame:CGRectMake(20, 50, 100, 100)];
    imageView.image=[self changeimagetocilce:[UIImage imageNamed:@"1.png"]];
    [self.view addSubview:imageView];
    
    
}
//将图片处理成圆的
-(id)changeimagetocilce:(UIImage*)image
{
    UIImage *finalImage = nil;
    UIGraphicsBeginImageContext(image.size);
    {
        CGContextRef ctx = UIGraphicsGetCurrentContext();
        CGAffineTransform trnsfrm = CGAffineTransformConcat(CGAffineTransformIdentity, CGAffineTransformMakeScale(1.0, -1.0));
        trnsfrm = CGAffineTransformConcat(trnsfrm, CGAffineTransformMakeTranslation(0.0, image.size.height));
        CGContextConcatCTM(ctx, trnsfrm);
        CGContextBeginPath(ctx);
        CGContextAddEllipseInRect(ctx, CGRectMake(0.0, 0.0, image.size.width, image.size.height));
        CGContextClip(ctx);
        CGContextDrawImage(ctx, CGRectMake(0.0, 0.0, image.size.width, image.size.height), image.CGImage);
        finalImage = UIGraphicsGetImageFromCurrentImageContext();
        UIGraphicsEndImageContext();
    }
    
    return finalImage;
}