iOS系统自带毛玻璃效果

UIImageView* imageview = [[UIImageViewalloc]initWithImage:[UIImageimageNamed:@"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.viewaddSubview:imageview];
   
    UIBlurEffect * blur = [UIBlurEffecteffectWithStyle:UIBlurEffectStyleDark];
    UIVisualEffectView * effectview = [[UIVisualEffectViewalloc]initWithEffect:blur];
    effectview.frame= CGRectMake(0,0, imageview.frame.size.width, imageview.frame.size.height);
    [imageview addSubview:effectview];
   
    UIButton *button = [UIButtonbuttonWithType:UIButtonTypeSystem];
    button.frame= CGRectMake(10,50,60,60);
    [button setTitle:@"btn"forState:UIControlStateNormal];

    [effectview.contentViewaddSubview:button];