ToHexString4.swift

func toHexString4(_ color:UIColor) -> String? {
    var cgColor:CGColor = color.cgColor
    if let name = cgColor.colorSpace?.name, name != CGColorSpace.sRGB {
        cgColor = color.cgColor.converted(to: CGColorSpace(name: CGColorSpace.sRGB)!, intent: .defaultIntent, options: nil)!
    }
    let ciColor = CIColor(cgColor: cgColor)
    return toHexString([ciColor.red, ciColor.green, ciColor.blue, ciColor.alpha])
}