How to get the RGB Code (INT) from an UIColor in Swift

Question

I would like to get the RGB Value of an UIColor in Swift:

let swiftColor = UIColor(red: 1, green: 165/255, blue: 0, alpha: 1)
println("RGB Value is:");
println(swiftColor.getRGB()); <<<<<< How to do that ?

In Java I would do it as follows:

Color cnew = new Color();
int iColor = cnew.rgb(1, 165/255, 0);
System.out.println(iColor);

How should I get this value?

Answer 1

The Java getRGB() returns an integer representing the color in the default sRGB color space (bits 24-31 are alpha, 16-23 are red, 8-15 are green, 0-7 are blue).

UIColor does not have such a method, but you can define your own:

extension UIColor {

    func rgb() -> Int? {
        var fRed : CGFloat = 0
        var fGreen : CGFloat = 0
        var fBlue : CGFloat = 0
        var fAlpha: CGFloat = 0
        if self.getRed(&fRed, green: &fGreen, blue: &fBlue, alpha: &fAlpha) {
            let iRed = Int(fRed * 255.0)
            let iGreen = Int(fGreen * 255.0)
            let iBlue = Int(fBlue * 255.0)
            let iAlpha = Int(fAlpha * 255.0)

            //  (Bits 24-31 are alpha, 16-23 are red, 8-15 are green, 0-7 are blue).
            let rgb = (iAlpha << 24) + (iRed << 16) + (iGreen << 8) + iBlue
            return rgb
        } else {
            // Could not extract RGBA components:
            return nil
        }
    }
}

Usage:

let swiftColor = UIColor(red: 1, green: 165/255, blue: 0, alpha: 1)
if let rgb = swiftColor.rgb() {
    print(rgb)
} else {
    print("conversion failed")
}

Note that this will only work if the UIColor has been defined in an "RGB-compatible" colorspace (such as RGB, HSB or GrayScale). It may fail if the color has been created from an CIColor or a pattern image, in that case nil is returned.

Remark: As @vonox7 noticed, the returned value can be negative on 32-bit platforms (which is also the case with the Java getRGB() method). If that is not wanted, replace Int by UInt or Int64.

The reverse conversion is

extension UIColor {
    convenience init(rgb: Int) {
        let iBlue = rgb & 0xFF
        let iGreen =  (rgb >> 8) & 0xFF
        let iRed =  (rgb >> 16) & 0xFF
        let iAlpha =  (rgb >> 24) & 0xFF
        self.init(red: CGFloat(iRed)/255, green: CGFloat(iGreen)/255,
                  blue: CGFloat(iBlue)/255, alpha: CGFloat(iAlpha)/255)
    }
}