public static string ImageFile2Base64(string filename)
        {
            if (!File.Exists(filename))
                return String.Empty;

            System.Drawing.Image image = System.Drawing.Image.FromFile(filename);

            return Image2Base64(image);
        }

        public static void Base642ImageFile(string base64, string filename)
        {
            try
            {
                System.Drawing.Image image = Base642Image(base64);
                System.Drawing.Bitmap newimage = new System.Drawing.Bitmap(image);
                image.Dispose();
                string dir = Path.GetDirectoryName(filename);
                if (!Directory.Exists(dir))
                    Directory.CreateDirectory(dir);
                newimage.Save(filename);
            }
            catch (Exception exc)
            { }
        }

        public static void Base642ImageFile(string base64, string filename, System.Drawing.Imaging.ImageFormat format)
        {
            System.Drawing.Image image = Base642Image(base64);
            image.Save(filename, format);
        }

        public static string Image2Base64(System.Drawing.Image image)
        {
            MemoryStream ms = new MemoryStream();
            image.Save(ms, System.Drawing.Imaging.ImageFormat.Png);
            Byte[] filedata = ms.ToArray();
            ms.Close();
            return Convert.ToBase64String(filedata);
        }

        public static System.Drawing.Image Base642Image(string base64)
        {
            Byte[] filedate = Convert.FromBase64String(base64);
            MemoryStream ms = new MemoryStream(filedate);
            System.Drawing.Image image = System.Drawing.Image.FromStream(ms);
            ms.Flush();
            ms.Close();
            System.Drawing.Image newimage = image.Clone() as System.Drawing.Image;
            image.Dispose();
            return newimage;
        }