给图片加阴影

- (void)viewDidLoad
{
    [super viewDidLoad];
    UIImage *img = [UIImage imageNamed:@"Icon.png"];
    UIImageView *imgView = [[UIImageView alloc] initWithImage:img];
    imgView.center = self.view.center;
    [[imgView layer] setShadowOffset:CGSizeMake(5, 5)]; // 阴影的范围
    [[imgView layer] setShadowRadius:2];                // 阴影扩散的范围控制
    [[imgView layer] setShadowOpacity:1];               // 阴影透明度
    [[imgView layer] setShadowColor:[UIColor brownColor].CGColor]; // 阴影的颜色
    [self.view addSubview:imgView];
}