space-ios/iOSClient/Extensions/UIColor+Extensions.swift

//
//  UIColor+adjust.swift
//  Nextcloud
//
//  Created by Marino Faggiana on 04/02/2020.
//  Copyright © 2020 Marino Faggiana. All rights reserved.
//
//  Author Marino Faggiana <marino.faggiana@nextcloud.com>
//
//  This program is free software: you can redistribute it and/or modify
//  it under the terms of the GNU General Public License as published by
//  the Free Software Foundation, either version 3 of the License, or
//  (at your option) any later version.
//
//  This program is distributed in the hope that it will be useful,
//  but WITHOUT ANY WARRANTY; without even the implied warranty of
//  MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
//  GNU General Public License for more details.
//
//  You should have received a copy of the GNU General Public License
//  along with this program.  If not, see <http://www.gnu.org/licenses/>.
//

import Foundation

extension UIColor {
    
    @objc convenience init?(hex: String) {

        let r, g, b, a: CGFloat
        
        if hex.hasPrefix("#") {
            
            let start = hex.index(hex.startIndex, offsetBy: 1)
            let hexColor = String(hex[start...])
            let scanner = Scanner(string: hexColor)
            var hexNumber: UInt64 = 0
            
            if hexColor.count == 6 && scanner.scanHexInt64(&hexNumber) {
                
                r = CGFloat((hexNumber & 0xff0000) >> 16) / 255.0
                g = CGFloat((hexNumber & 0x00ff00) >> 8) / 255.0
                b = CGFloat(hexNumber & 0x0000ff) / 255.0

                self.init(red: r, green: g, blue: b, alpha: 1)
                return
                
            } else if hexColor.count == 7 && scanner.scanHexInt64(&hexNumber) {
                    
                r = CGFloat((hexNumber & 0xff000000) >> 24) / 255
                g = CGFloat((hexNumber & 0x00ff0000) >> 16) / 255
                b = CGFloat((hexNumber & 0x0000ff00) >> 8) / 255
                a = CGFloat(hexNumber & 0x000000ff) / 255

                self.init(red: r, green: g, blue: b, alpha: a)
                return
            }
        }
        
        return nil
    }
    
    @objc func lighter(by percentage: CGFloat = 30.0) -> UIColor? {
        return self.adjust(by: abs(percentage) )
    }

    @objc func darker(by percentage: CGFloat = 30.0) -> UIColor? {
        return self.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 self.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
        }
    }
    
    @objc func isTooLight() -> Bool {
        
        var white: CGFloat = 0.0
        self.getWhite(&white, alpha: nil)
        if white == 1 { return true }
        
        guard let components = cgColor.components, components.count > 2 else {return false}
        let brightness = ((components[0] * 299) + (components[1] * 587) + (components[2] * 114)) / 1000
        return (brightness > 0.95)
    }
    
    @objc func isTooDark() -> Bool {
        
        var white: CGFloat = 0.0
        self.getWhite(&white, alpha: nil)
        if white == 0 { return true }
        
        guard let components = cgColor.components, components.count > 2 else {return false}
        let brightness = ((components[0] * 299) + (components[1] * 587) + (components[2] * 114)) / 1000
        return (brightness < 0.05)
    }
    
    func isLight(threshold: Float = 0.7) -> Bool {
        let originalCGColor = self.cgColor

        // Now we need to convert it to the RGB colorspace. UIColor.white / UIColor.black are greyscale and not RGB.
        // If you don't do this then you will crash when accessing components index 2 below when evaluating greyscale colors.
        let RGBCGColor = originalCGColor.converted(to: CGColorSpaceCreateDeviceRGB(), intent: .defaultIntent, options: nil)
        guard let components = RGBCGColor?.components else { return false }
        guard components.count >= 3 else { return false }

        let brightness = Float(((components[0] * 299) + (components[1] * 587) + (components[2] * 114)) / 1000)
        return (brightness > threshold)
    }
}