swift - 每次用户选择另一种颜色时如何更改对比度？

Question

我知道在 JavaScript 中有一个函数可以根据当前选择的颜色改变对比度:

---

function getHigherContrast(r, g, b) {
    const yiq = ((r * 299) + (g * 587) + (b * 114)) / 1000;
    return (yiq >= 128) ? '#000000' : '#FFFFFF';
}

如何将此函数重写为 Swift-Code，以便每次用户选择另一种颜色时对比度都会发生变化:

---

override func viewDidLoad() {
    super.viewDidLoad()

    self.view.addSubview(colorPicker)
    colorPicker.translatesAutoresizingMaskIntoConstraints = false
    colorPicker.trailingAnchor.constraint(equalTo: self.view.layoutMarginsGuide.trailingAnchor).isActive = true
    colorPicker.leadingAnchor.constraint(equalTo: self.view.layoutMarginsGuide.leadingAnchor).isActive = true
    colorPicker.topAnchor.constraint(equalTo: self.view.layoutMarginsGuide.topAnchor).isActive = true
    colorPicker.bottomAnchor.constraint(equalTo: self.view.bottomAnchor).isActive = true

    navigationItem.rightBarButtonItem = UIBarButtonItem(barButtonSystemItem: .done, target: self, action:#selector(handleDone(sender:)))

    colors.append((colorTitle: "rot", color: UIColor.red))
    colors.append((colorTitle: "gelb", color: UIColor.yellow))
    colors.append((colorTitle: "grün", UIColor.green))
    colors.append((colorTitle: "schwarz", UIColor.black))

    colorPicker.delegate = self
    colorPicker.dataSource = self
}

func numberOfComponents(in pickerView: UIPickerView) -> Int {
    return 1
}

func pickerView(_ pickerView: UIPickerView, numberOfRowsInComponent component: Int) -> Int {
    return colors.count
}

func pickerView(_ pickerView: UIPickerView, attributedTitleForRow row: Int, forComponent component: Int) -> NSAttributedString? {
    return NSAttributedString(string: colors[row].colorTitle, attributes: [NSAttributedStringKey.foregroundColor: colors[row].color])
}

@objc func handleDone(sender: AnyObject?) {
    if let d = delegate {
        d.colorPicked(color: colors[colorPicker.selectedRow(inComponent: 0)].color)
    }
    dismiss(animated: true)
}

---

Here是该类的完整源代码。

Answer 1

你可以试试

func getHigherContrast(r:Int, g:Int, b:Int) -> UIColor {
   let yiq = ((r * 299) + (g * 587) + (b * 114)) / 1000
   return yiq >= 128 ?  UIColor.black : UIColor.white
}