[UIColor+Extensions] UIColor extensions #extension #iOS

UIColor+Extensions.swift

//
//  UIColor+Extensions.swift
//
//  Created by Jay Lee on 05/05/2019.
//  Copyright © 2019 Jay Lee <jaeho.lee@snu.ac.kr>
//  This work is free. You can redistribute it and/or modify it under the
//  terms of the Do What The Fuck You Want To Public License, Version 2,
//  as published by Sam Hocevar. See http://www.wtfpl.net/ for more details.
//

import UIKit

extension UIColor {

  convenience init(red: Int, green: Int, blue: Int) {
    assert(red >= 0 && red <= 255, "Invalid red component")
    assert(green >= 0 && green <= 255, "Invalid green component")
    assert(blue >= 0 && blue <= 255, "Invalid blue component")

    self.init(red: CGFloat(red) / 255.0, green: CGFloat(green) / 255.0, blue: CGFloat(blue) / 255.0, alpha: 1.0)
  }


  convenience init(rgb: Int) {
    self.init(
      red: (rgb >> 16) & 0xFF,
      green: (rgb >> 8) & 0xFF,
      blue: rgb & 0xFF
    )
  }


  func lighter(by percentage: CGFloat = 30.0) -> UIColor? {
    return adjust(by: abs(percentage))
  }


  func darker(by percentage: CGFloat = 30.0) -> UIColor? {
    return adjust(by: -1 * abs(percentage))
  }


  func adjust(by percentage: CGFloat = 30.0) -> UIColor? {
    var red: CGFloat = 0, green: CGFloat = 0, blue: CGFloat = 0, alpha: CGFloat = 0
    if getRed(&red, green: &green, blue: &blue, alpha: &alpha) {
      return UIColor(red: min(red + percentage/100, 1.0),
                     green: min(green + percentage/100, 1.0),
                     blue: min(blue + percentage/100, 1.0),
                     alpha: alpha)
    } else {
      return nil
    }
  }
}