How to read the red, green, blue, and alpha color components from a UIColor

Paul Hudson    February 13th 2018    @twostraws

Creating a UIColor from red, green, blue, and alpha (RGBA) is easy enough:

let color = UIColor(red: 0.8, green: 0.1, blue: 0.5, alpha: 1)

But when you want to read those values back, you need to do a little more work. UIColor has a built-in method called getRed(), which unpacks the RGBA values into variable floats – you need to create four variables first, then pass them in by reference:

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)

When that runs, red will have 0.8, green will have 0.1, and so on.

Because this is a pain to use you might find it best to wrap it up in an extension:

extension UIColor {
    var rgba: (red: CGFloat, green: CGFloat, blue: CGFloat, alpha: CGFloat) {
        var red: CGFloat = 0
        var green: CGFloat = 0
        var blue: CGFloat = 0
        var alpha: CGFloat = 0
        getRed(&red, green: &green, blue: &blue, alpha: &alpha)

        return (red, green, blue, alpha)
    }
}

Now you can use color.rgba to get back a tuple of all four color values.

Available from iOS 5.0

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