BitmapImage to Bitmap ---WPF

/// <summary>
        //BitmapImage to Bitmap
        /// </summary>
        /// <param name="bitmapImage">需转化的BitmapImage</param>
        /// <returns>Bitmap</returns>
        public static System.Drawing.Bitmap BitmapImage2Bitmap(BitmapImage bitmapImage)
        {
            using (System.IO.MemoryStream outStream = new System.IO.MemoryStream())
            {
                BitmapEncoder enc = new BmpBitmapEncoder();
                enc.Frames.Add(BitmapFrame.Create(bitmapImage));
                enc.Save(outStream);
                System.Drawing.Bitmap bitmap = new System.Drawing.Bitmap(outStream);

                return bitmap;
            }
        }