App置灰或则页面置灰

1.页面或则view置灰的方式，如果是整个App置灰就设置view为window

///1.第一种是给view上添加一个置灰的view
    @objc private func addGrayViewOnTop(){
        let overlay = UIView.init(frame: stackView.bounds)
        overlay.translatesAutoresizingMaskIntoConstraints = false
        overlay.backgroundColor = .lightGray
        overlay.layer.compositingFilter = "saturationBlendMode"
        overlay.isUserInteractionEnabled = false
        stackView.addSubview(overlay)

    }
    
    ///2.用滤镜的方式  如果需要整个App置灰，就挂在Window上  需要哪里置灰挂在哪里
    @objc private func useFilterMethod(){
        let color = UIColor.lightGray
        var red: CGFloat = 0
        var green: CGFloat = 0
        var blue: CGFloat = 0
        var alpha: CGFloat = 0
        color.getRed(&red, green: &green, blue: &blue, alpha: &alpha)
        guard let filter = CIFilter.init(name: "colorMonochrome") else { return }
        filter.setValue([red, green, blue, alpha], forKey: "inputColor")
        filter.setValue(0, forKey: "inputBias")
        filter.setValue(1, forKey: "inputAmount")
        stackView.layer.filters = [filter]
    }