How to convert a UIColor to a black and white UIColor - swift

Question

I am setting the background color of my label, but I would like to have the color be the black and white UIColor instead of the original UIColor.
self.MyLabel.backgroundColor = self.selectedColors.color

Answer 1

Looks like you'll need to convert your colour to grayscale.
While you can do this by averaging the R, G and B components of the colour, apple actually provide a nice method to grab the grayscale value:
func getWhite(_ white: UnsafeMutablePointer<CGFloat>?,
alpha: UnsafeMutablePointer<CGFloat>?) -> Bool
So to use this, you would first extract the grayscale colour and then init a new UIColor:
let originalColor = self.selectedColors.color
var white: CGFloat = 0
var alpha: CGFloat = 0
guard originalColor.getWhite(&white, alpha: &alpha) else {
// The color couldn't be converted! Handle this unexpected error
return
}
let newColor = UIColor(white: white, alpha: alpha)
self.MyLabel.backgroundColor = newColor

Answer 2

By thanks of #Sam answer, I write an extension for UIColor:
extension UIColor {
var grayScale: UIColor? {
var white: CGFloat = 0
var alpha: CGFloat = 0
guard self.getWhite(&white, alpha: &alpha) else {
return nil
}
return UIColor(white: white, alpha: alpha)
}
}
You can use it like this:
var grayScaleColorOfRed = UIColor.red.grayScale ?? UIColor.grey