Generate a color from a string (deterministically)

UIColor+String.swift

import UIKit

extension UIColor {
    /// Generate a color from the given string deterministically.
    ///
    /// Generated colors are *not* evenly distributed in the HSL color space, but you and/or your users also probably won't be able to tell.
    convenience init(_ string: String, saturation: Double = 0.8, brightness: Double = 0.8) {
        let seed = Double.pi // Can be any positive irrational number. Pi was chosen for flavor.
        let hash = string
            .compactMap { $0.unicodeScalars.first?.value.byteSwapped }
            .map(Double.init)
            .reduce(seed) { (hash, unicodeValue) in
                return (hash * seed * unicodeValue)
                    .truncatingRemainder(dividingBy: 360)
            }

        let hue = hash / 360

        self.init(hue: CGFloat(hue), saturation: CGFloat(saturation), brightness: CGFloat(brightness), alpha: 1.0)
    }
}

// These should all look different.
UIColor("")
UIColor("0")
UIColor("00")
UIColor("000")
UIColor("1")
UIColor("1", saturation: 0.4)

// Long and Unicode strings are fine, too.
UIColor("以呂波耳本部止千利奴流乎和加餘多連曽津祢那良牟有為能於久耶万計不己衣天阿佐伎喩女美之恵比毛勢須")

// Colors are deterministic.
assert(UIColor("apples") == UIColor("apples"))
assert(UIColor("apples") != UIColor("oranges"))
assert(UIColor("apples", saturation: 1.0) != UIColor("apples", saturation: 0.9))
assert(UIColor("apples", brightness: 1.0) != UIColor("apples", brightness: 0.9))