问将两个UIImages合并为一个

EN

extension UIImage {
    func overlayWith(image: UIImage, posX: CGFloat, posY: CGFloat, topImageSize: CGSize,
                     combinedImage: @escaping (UIImage) -> Void) {
        DispatchQueue.global(qos: .userInteractive).async {
            let newWidth = self.size.width < posX + image.size.width ? posX + image.size.width : self.size.width
            let newHeight = self.size.height < posY + image.size.height ? posY + image.size.height : self.size.height
            let newSize = CGSize(width: newWidth, height: newHeight)

            UIGraphicsBeginImageContextWithOptions(newSize, false, 0.0)
            self.draw(in: CGRect(origin: CGPoint.zero, size: self.size))
            image.draw(in: CGRect(origin: CGPoint(x: posX, y: posY), size: topImageSize))
            let newImage = UIGraphicsGetImageFromCurrentImageContext()!
            UIGraphicsEndImageContext()

            DispatchQueue.main.async {
                combinedImage(newImage)
            }
        }
    }
}