Generates dark UIColor from a numeric string provided a radix

DarkColorFromNumeric.swift

//
//  DarkColorFromHash.swift
//
//  Created by Ashton Meuser on 2017-04-26.
//  Copyright © 2017 Ashton Meuser. All rights reserved.
//

import Foundation
import UIKit

extension String {
    func trimNumeric(for bits: Int, radix: Int = 10) -> String {
        let max: Double = pow(2.0, Double(bits)) // Maximum representable 
        let cuttoff = Int(log(max) / log(Double(radix)))
        return String(self.suffix(cuttoff))
    }
}

static func darkColor(from numeric: String, radix: Int = 10) -> UIColor {
    let trimmed = numeric.trimNumeric(for: 32, radix: radix) // Avoid overflow
    guard let number = UInt32(trimmed, radix: radix) else {
        return UIColor.clear // If radix can't be represented by string
    }
    let hue = CGFloat(number % 256) / 256.0 // Bits 0 to 7
    let saturation = CGFloat(number >> 8 % 128 + 128) / 256.0 // Bits 8 to 11
    let brightness = CGFloat(number >> 12 % 256) / 256.0 // Bits 12 to 19
    return UIColor(hue: hue, saturation: saturation, brightness: brightness, alpha: 1.0)
}