UIColor+Grayscale.swift

extension UIColor {
	
	public var grayscale: UIColor {
		
		var (red, green, blue, alpha) = (CGFloat(0), CGFloat(0), CGFloat(0), CGFloat(0))
		
		if self.getRed(&red, green: &green, blue: &blue, alpha: &alpha) {
			
			// https://en.wikipedia.org/wiki/Grayscale
			return UIColor(white: red * 0.299 + green * 0.587 + blue * 0.114, alpha: alpha)
		}
		
		return self
	}
}