图片与base64的互转

 /// <summary>
        /// 把图片转换到文本信息
        /// </summary>
        /// <param name="imagePath">图片的路径</param>
        /// <param name="savePath">文本存储路径</param> 

public void GetImageToString(string imagePath,string savePath)
        {
            Stream s = File.Open(imagePath, FileMode.Open);
            int leng = 0;
            if (s.Length < Int32.MaxValue)     //防止图片太大了
            leng = (int)s.Length;
            byte[] by = new byte[leng];        //声明字节数组

            MemoryStream s = new MemoryStream(by);    //内存中声明一个流       
            s.Read(by, 0, (int)s.Length);//把图片读到字节数组中
            s.Close();

            string str = Convert.ToBase64String(by);//把字节数组转换成字符串
            StreamWriter sw = File.CreateText(savePath);//存入savePath文件
            sw.Write(str);
            sw.Close();
            sw.Dispose();
        }

         /// <summary>
        /// 把字符串还原成图片
        /// </summary>
        /// <param name="path"></param>
        /// <returns>图片</returns>

        public Image GetImageFromString(string stringPath)
        {
            StreamReader sr = new StreamReader(stringPath);
            string s = sr.ReadToEnd();
            sr.Close();
            byte[] buf = Convert.FromBase64String(s);//把字符串读到字节数组中

            MemoryStream ms = new MemoryStream(buf);
            System.Drawing.Image img = System.Drawing.Image.FromStream(ms);
            img.Save("12.gif", System.Drawing.Imaging.ImageFormat.Gif);  //保存成图片
            ms.Close();
            ms.Dispose();
            return img;
        }