self.view.backgroundColor = [UIColor redColor];

    UIImageView *imageView = [[UIImageView alloc] initWithImage:[UIImage imageNamed:@""]];

    imageView.frame = CGRectMake(100, 100, 100, 100);

    [self.view addSubview:imageView];

//UIRectCornerAllCorners 可改为四个角     

   UIRectCornerTopLeft    ,

    UIRectCornerTopRight    ,

    UIRectCornerBottomLeft  ,

    UIRectCornerBottomRight ,

    UIBezierPath *bezierPath = [UIBezierPath bezierPathWithRoundedRect:imageView.bounds byRoundingCorners:UIRectCornerAllCorners cornerRadii:CGSizeMake(imageView.frame.size.height / 2.0, imageView.frame.size.height / 2.0)];

    CAShapeLayer *shapeLayer = [CAShapeLayer layer];

    shapeLayer.path = bezierPath.CGPath;

   imageView.layer.mask = shapeLayer;