IOS实现高斯模糊

       UIBlurEffect *blur = [UIBlurEffect effectWithStyle:UIBlurEffectStyleLight];

        UIVisualEffectView *effectview = [[UIVisualEffectView alloc] initWithEffect:blur];
        effectview.frame = CGRectMake(0,
0, imageview.size.width/2,
300);
        
        [imageview addSubview:effectview];