UIColor+TextColor

UIColor-TextColor.swift

import Foundation
import UIKit

extension UIColor {
    convenience init(hex: String) {
        let scanner = Scanner(string: hex)
        scanner.scanLocation = 1
        var rgb: UInt64 = 0
        scanner.scanHexInt64(&rgb)
        self.init(rgb: Int(rgb))
    }

    convenience init(rgb: Int) {
        let red = (rgb >> 16) & 0xFF
        let green = (rgb >> 8) & 0xFF
        let blue = rgb & 0xFF
        self.init(red: CGFloat(red) / 255.0, green: CGFloat(green) / 255.0, blue: CGFloat(blue) / 255.0, alpha: 1.0)
    }

    var textColor: UIColor {
        var hue: CGFloat = 0, saturation: CGFloat = 0, brightness: CGFloat = 0, alpha: CGFloat = 0
        getHue(&hue, saturation: &saturation, brightness: &brightness, alpha: &alpha)
        return UIColor(hue: 0, saturation: 0, brightness: luminance > 0.5 ? 0 : 1, alpha: alpha)
    }

    var luminance: CGFloat {
        var red: CGFloat = 0, green: CGFloat = 0, blue: CGFloat = 0, alpha: CGFloat = 0
        getRed(&red, green: &green, blue: &blue, alpha: &alpha)
        let vs = [red,green,blue].map { $0 <= 0.03928 ? $0 / 12.92 : pow(($0 + 0.055) / 1.055, 2.4) }
        return vs[0] * 0.2126 + vs[1] * 0.7152 + vs[2] * 0.0722
    }
}

func label(_ color: UIColor) -> UILabel {
    let lb = UILabel(frame: CGRect(origin: .zero, size: CGSize(width: 60, height: 20)))
    lb.backgroundColor = color
    lb.text = "CHAMP"
    lb.textColor = color.textColor
    lb.font = UIFont.systemFont(ofSize: 13)
    lb.textAlignment = .center
    lb.layer.cornerRadius = 10
    lb.clipsToBounds = true
    return lb
}

let lb1 = label(UIColor(rgb: 0xffffff))
let lb2 = label(UIColor(rgb: 0x000000))
let lb3 = label(UIColor(rgb: 0xe3e3e3))
let lb4 = label(UIColor(hex: "#0x3671f1"))
let lb5 = label(UIColor(rgb: 0xffd150))
let lb6 = label(UIColor(rgb: 0xf05322))
let lb7 = label(UIColor(rgb: 0xf8e71c))
let lb8 = label(UIColor(red: 255 / 255.0, green: 195 / 255.0, blue: 48 / 255.0, alpha: 1))
let lb9 = label(UIColor(red: 54 / 255.0, green: 81 / 255.0, blue: 241 / 255.0, alpha: 1))