Get a contrasting UIColor for a background UIColor that could be used for text (for eg.)

UIColor+contrasting.swift

import UIKit

extension UIColor {
   private struct ColorComponents {
      var r: CGFloat = 0.0
      var g: CGFloat = 0.0
      var b: CGFloat = 0.0
      var a: CGFloat = 0.0
   }

   private func components() -> ColorComponents {
      var result = ColorComponents()
      self.getRed(&result.r, green: &result.g, blue: &result.b, alpha: &result.a)
      return result
   }
   
   func contrastingTextColor() -> UIColor {
      if self == UIColor.clear {
         return .black
      }

      let rgbColor = self.components()

      // Counting the perceptive luminance - human eye favors green color...
      let avgGray: CGFloat = 1 - (0.299 * rgbColor.r + 0.587 * rgbColor.g + 0.114 * rgbColor.b)
      return avgGray > 0.5 ? .white : .black
   }
}