iOS系統自帶毛玻璃效果

UIImageView * imageview = [[UIImageView alloc] initWithImage:[UIImage imageNamed:@"屏幕快照 2015-12-18 下午10.51.33"]];
    imageview.userInteractionEnabled = YES;
    imageview.contentMode = UIViewContentModeScaleAspectFit;
    imageview.frame = CGRectMake(0, 0, 375, 668);
    [self.view addSubview:imageview];
   
    UIBlurEffect * blur = [UIBlurEffect effectWithStyle:UIBlurEffectStyleDark];
    UIVisualEffectView * effectview = [[UIVisualEffectView alloc] initWithEffect:blur];
    effectview.frame = CGRectMake(0, 0, imageview.frame.size.width, imageview.frame.size.height);
    [imageview addSubview:effectview];
   
    UIButton *button = [UIButton buttonWithType:UIButtonTypeSystem];
    button.frame = CGRectMake(10, 50, 60, 60);
    [button setTitle:@"btn" forState:UIControlStateNormal];

    [effectview.contentView addSubview:button];