Ios 如何向CALayer添加隐藏到自定义内容的阴影

我正在尝试将阴影添加到遮罩的

UIView

（来自

UIImage

），但我相信，因为视图被遮罩到边界，

masksToBounds=YES

阴影不会显示

如果确实是这样，那么我如何才能在蒙版图像周围绘制阴影呢

-(UIView *)modifyViewWithMask:(UIView *)view
{
    view.alpha = 0.5;
    UIView *blackView = [[UIView alloc] initWithFrame:view.bounds];
    blackView.autoresizingMask = UIViewAutoresizingFlexibleHeight | UIViewAutoresizingFlexibleWidth;
    blackView.backgroundColor = [UIColor colorWithWhite:0 alpha:0.3];
    [view addSubview:blackView];


    UIImage* bubbleImage = [UIImage imageNamed:@"Bubble"];

    CALayer* mask = [CALayer layer];
    mask.contents = (id)[bubbleImage CGImage];
    mask.frame = CGRectMake(0, 0, view.frame.size.width, view.frame.size.height);
    view.layer.mask = mask;
    view.layer.masksToBounds = YES;


    view.layer.shadowColor = [UIColor blackColor].CGColor;
    view.layer.shadowOffset = CGSizeMake(10, 10);
    view.layer.shadowRadius = 10;
    view.layer.shadowOpacity = 1;


}