Expressing RGB Colors as Arrays in Swift

UIColor+Array.swift

//Cleanly instantiate UIColors using 1 or 3 Int, Double, Float, or CGFloat Values

//UIColor convience initializer UIColor(4, 20, 69)
//UIColor convience initializer for gray(all three values the same) UIColor(69)

//Instantiate gray from a number: 210.rgbTriple()
//Instantiate color from an array of numbers:[40, 33, 60].rgbColor() 

//Optionally express an alpha value 
//UIColor(4, 20, 69, 0.4)
//[69, 0.2].rgbColor()

import Foundation
protocol RGBNormalized {
    var rgb:CGFloat { get }
    var cgFloat:CGFloat { get }
}

extension RGBNormalized {
    func rgbTriple() -> UIColor { return UIColor.init(self) }
}

extension Int:RGBNormalized {
    var rgb:CGFloat { return CGFloat(self) / 255.0 }
    var cgFloat:CGFloat { return CGFloat(self) }
}

extension Double:RGBNormalized {
    var rgb:CGFloat { return CGFloat(self / 255.0) }
    var cgFloat:CGFloat { return CGFloat(self) }
}

extension Float:RGBNormalized {
    var rgb:CGFloat { return CGFloat(self / 255.0) }
    var cgFloat:CGFloat { return CGFloat(self) }
}

extension CGFloat {
    var rgb:CGFloat { return self / 255.0 }
    var cgFloat:CGFloat { return CGFloat(self) }
}

extension Array where Element == RGBNormalized {
    func rgbColor() -> UIColor {
        switch count {
        case 1: return UIColor(self[0])
        case 2: return UIColor(self[0], self[1])
        case 3: return UIColor(self[0], self[1], self[2])
        case 4: return UIColor(self[0], self[1], self[2], self[3])
        default: return UIColor.black
        }
    }
}

extension UIColor {
    convenience init(_ r:RGBNormalized, _ g:RGBNormalized, _ b:RGBNormalized, _ a:RGBNormalized = 1.0) {
        self.init(red: r.rgb, green: g.rgb, blue: b.rgb, alpha: a.cgFloat)
    }
    
    convenience init(_ v:RGBNormalized, _ a:RGBNormalized = 1.0) {
        let value:CGFloat = v.rgb
        self.init(red: value, green: value, blue: value, alpha: a.cgFloat)
    }
}