iOS8之后有一个类 UIVisualEffectView

// 毛玻璃    UIImageView *img = [[UIImageView alloc] initWithFrame:CGRectMake(0, 0, WIDTH, HEIGHT)];    img.userInteractionEnabled = YES;    img.image = [UIImage imageNamed:@"effect"];        [self.view addSubview:img];//    UIBlurEffectStyleExtraLight,//    UIBlurEffectStyleLight,//    UIBlurEffectStyleDark    UIBlurEffect *blur = [UIBlurEffect effectWithStyle:UIBlurEffectStyleLight];    UIVisualEffectView *effectview = [[UIVisualEffectView alloc] initWithEffect:blur];    effectview.frame = CGRectMake(0, 0, WIDTH, HEIGHT);    effectview.userInteractionEnabled = YES;    UITapGestureRecognizer *tap = [[UITapGestureRecognizer alloc] initWithTarget:self action:@selector(click)];    [effectview addGestureRecognizer:tap];    effectview.alpha = 1.0; // 根据需要设置渲染的程度    [self.view addSubview:effectview];