A extension for UIColor that creates a UIColor from a hex code.

UIColor.swift

import UIKit

public extension UIColor {
    
    /// Initialize a color from a hex value. Optionally include an alpha value (default is 1).
    ///
    /// - Parameters:
    ///   - hex: The integer that will be resolved to the red, green and blue component.
    ///   - alpha: The alpha value of the color.
    public convenience init?(hex: UInt, alpha: CGFloat = 1) {
        
        guard hex <= 0xFFFFFF else {
            // Value is out of range; an invalid color
            return nil
        }
        
        let red = CGFloat((hex & 0xFF0000) >> 16)/255
        let green = CGFloat((hex & 0x00FF00) >> 8)/255
        let blue = CGFloat(hex & 0x0000FF)/255
        self.init(red: red, green: green, blue: blue, alpha: alpha)
    }
    
    /// Initalize a UIColor from a hex string that optionally includes an alpha component.
    /// The hex string must be prefixed with #.
    ///
    /// - Parameter hex: The hex value as a string representing RGB or RGBA, prefixed with #.
    public convenience init?(hex: String) {
        
        let includesAlphaComponent = (hex.count == 9)
        guard hex.hasPrefix("#"), includesAlphaComponent || hex.count == 7 else {
            // Invalid hex format
            return nil
        }
        
        let start = hex.index(hex.startIndex, offsetBy: 1)
        let hexColor = String(hex[start...])
        
        let scanner = Scanner(string: hexColor)
        var hexNumber: UInt64 = 0
        
        guard scanner.scanHexInt64(&hexNumber) else {
            // Invalid hex number
            return nil
        }

        let alpha = includesAlphaComponent ? CGFloat(hexNumber & 0xFF) / 255 : 1
        let hex = includesAlphaComponent ? UInt(hexNumber >> 8) : UInt(hexNumber)
        self.init(hex: hex, alpha: alpha)
    }
    
    /// Returns a color with brightness set to be 50% (round robin) off from the source color.
    /// In other words, the resulting color with be perfectly harmonious and easily visible together with the source color.
    ///
    /// - Returns: an harmonious color with inverted brightness.
    func contrastingColor() -> UIColor {
        var hue: CGFloat = 1
        var saturation: CGFloat = 1
        var brightness: CGFloat = 1
        var alpha: CGFloat = 1
        assert(getHue(&hue, saturation: &saturation, brightness: &brightness, alpha: &alpha), "Color is not UIColor.getHue compatible.")
        return UIColor(hue: hue, saturation: saturation, brightness: ((brightness + 0.5) % 1), alpha: alpha)
    }

}