Snippet of the Week: Lighter and Darker Colors

Playgrounds.swift

import UIKit
import PlaygroundSupport

public extension UIColor {
    public func hsba() -> (hue: CGFloat, saturation: CGFloat, brightness: CGFloat, alpha: CGFloat)? {
        var hue: CGFloat = .nan, saturation: CGFloat = .nan, brightness: CGFloat = .nan, alpha: CGFloat = .nan
        guard self.getHue(&hue, saturation: &saturation, brightness: &brightness, alpha: &alpha) else {
            return nil
        }
        return (hue: hue, saturation: saturation, brightness: brightness, alpha: alpha)
    }
    
    public func changedBrightness(byPercentage perc: CGFloat) -> UIColor? {
        if perc == 0 {
            return self.copy() as? UIColor
        }
        guard let hsba = hsba() else {
            return nil
        }
        let percentage: CGFloat = min(max(perc, -1), 1)
        let newBrightness = min(max(hsba.brightness + percentage, -1), 1)
        return UIColor(hue: hsba.hue, saturation: hsba.saturation, brightness: newBrightness, alpha: hsba.alpha)
    }
    
    public func lightened(byPercentage percentage: CGFloat = 0.1) -> UIColor? {
        return changedBrightness(byPercentage: percentage)
    }
    
    public func darkened(byPercentage percentage: CGFloat = 0.1) -> UIColor? {
        return changedBrightness(byPercentage: -percentage)
    }
    
    public func changedSaturation(byPercentage perc: CGFloat) -> UIColor? {
        if perc == 0 {
            return self.copy() as? UIColor
        }
        guard let hsba = hsba() else {
            return nil
        }
        let percentage: CGFloat = min(max(perc, -1), 1)
        let newSaturation = min(max(hsba.saturation + percentage, -1), 1)
        return UIColor(hue: hsba.hue, saturation: newSaturation, brightness: hsba.brightness, alpha: hsba.alpha)
    }
    
    public func tinted(byPercentage percentage: CGFloat = 0.1) -> UIColor? {
        return changedSaturation(byPercentage: percentage)
    }
    
    public func shaded(byPercentage percentage: CGFloat = 0.1) -> UIColor? {
        return changedSaturation(byPercentage: -percentage)
    }
}

let stackView1 = UIStackView(frame: CGRect(x: 0, y: 0, width: 500, height: 200))
stackView1.axis = .horizontal
stackView1.distribution = .fillEqually

var views1: [UIView] = []
let color1 = UIColor.purple.darkened(byPercentage: 0.2)!
for i in 0...4 {
    let subcolor = color1.lightened(byPercentage: CGFloat(i) * 0.1)
    let subview = UIView(frame: CGRect(x: 1, y: 1, width: 1, height: 1))
    subview.backgroundColor = subcolor
    views1 += [subview]
    stackView1.addArrangedSubview(subview)
}

PlaygroundPage.current.liveView = stackView1