高斯模糊效果

UIBlurEffect *effect = [UIBlurEffect effectWithStyle:UIBlurEffectStyleLight];
    UIVisualEffectView *effectView = [[UIVisualEffectView alloc] initWithEffect:effect];
    effectView.frame = CGRectMake(0, 0, SCREEN_WIDTH, SCREEN_HEIGHT - 64);
    // 加上以下代码可以使毛玻璃特效更明亮点
    UIVibrancyEffect *vibrancyView = [UIVibrancyEffect effectForBlurEffect:effect];
    UIVisualEffectView *visualEffectView = [[UIVisualEffectView alloc] initWithEffect:vibrancyView];
    visualEffectView.translatesAutoresizingMaskIntoConstraints = NO;
    [effectView.contentView addSubview:visualEffectView];
    [self.view addSubview:effectView];