Extension of UIImage to give overlay to an image.

Overlay.swift

extension UIImage {
    func overlayed(with overlay: UIImage) -> UIImage? {
        defer {
            UIGraphicsEndImageContext()
        }
        UIGraphicsBeginImageContextWithOptions(size, false, scale)
        self.draw(in: CGRect(origin: .zero, size: size))
        overlay.draw(in: CGRect(origin: .zero, size: size))
        if let image = UIGraphicsGetImageFromCurrentImageContext() {
            return image
        }
        return nil
    }
}