Determining text color from the background color in Swift?

Question

I am making a color picker app in Swift and I need the text to adapt to the background color.

I have text on a UIView that is black by default and I would like it to turn lighter if there is a darker background color and to make the text darker if there is a lighter background color to make the text more readable.

Here are some screenshots:

Hardly readable text (First image)

Hardly readable text (Second image)

If it is possible I would be thankful for your reply.

Answer 1

You can do something like:

extension UIColor
{
    var isDarkColor: Bool {
        var r, g, b, a: CGFloat
        (r, g, b, a) = (0, 0, 0, 0)
        self.getRed(&r, green: &g, blue: &b, alpha: &a)
        let lum = 0.2126 * r + 0.7152 * g + 0.0722 * b
        return  lum < 0.50
    }
}

Which will calculate the luminance of the color and determine if it's above a certain threshold. Then say myLabel.textColor = view.backgroundColor?.isDarkColor == true ? .white : .black