protected void Page_Load(object sender, EventArgs e)
    {
     Encoding gb = Encoding.GetEncoding("gb2312");
 
         //调用函数产生4个随机数字编码
         object[] bytes = CreateRegionCode(4);
 
        
         string str1 = bytes[0].ToString();
         string str2 = bytes[1].ToString();
         string str3 = bytes[2].ToString();
         string str4 = bytes[3].ToString();
 
         //输出的控制台
       
         // Response.Write(str1 + str2 + str3 + str4);
        //  return;

         string srs = str1 + str2 + str3 + str4;
         Bitmap srBmp = srBitmap(srs);
         System.IO.MemoryStream srMS = new System.IO.MemoryStream();
         srBmp.Save(srMS, System.Drawing.Imaging.ImageFormat.Gif);
         Response.ClearContent();
         Response.ContentType = "image/gif";
         Response.BinaryWrite(srMS.ToArray());
         srBmp.Dispose();

    }

     /// <summary>
     /// 根据指定参数返回BitMap对象
     /// 引用如下：
     /// using System.Drawing;
     /// 调用例子如下：
     ///     eg1、保存为图象文件为
     ///     Bitmap srBmp = srBitmap(srs);
     ///     srBmp.Save(Directory.GetCurrentDirectory() + "\\srs.gif", System.Drawing.Imaging.ImageFormat.Gif);
     ///     srBmp.Dispose();
     ///     eg2。网页中调用方式如下
     ///     Bitmap srBmp = srBitmap(srs);
     ///     System.IO.MemoryStream srMS = new System.IO.MemoryStream();
     ///     srBmp.Save(srMS,System.Drawing.Imaging.ImageFormat.Gif);
     ///     Response.ClearContent();
     ///     Response.ContentType = "image/gif";
     ///     Response.BinaryWrite(srMS.ToArray());
     ///     srBmp.Dispose();
     /// </summary>
     /// <param name="srs"></param>
     /// <returns></returns>

 public static Bitmap srBitmap(string srs)
     {
         //定义图片弯曲的角度
        int srseedangle = 40;
        //定义图象
        Bitmap srBmp = new Bitmap(srs.Length * 20, 30);
         //画图
         Graphics srGraph = Graphics.FromImage(srBmp);
         //清空图象
         srGraph.Clear(Color.AliceBlue);
         //给图象画边框
         srGraph.DrawRectangle(new Pen(Color.Black, 0), 0, 0, srBmp.Width - 1, srBmp.Height - 1);
         //定义随即数
         Random srRandom = new Random();
         //定义画笔
         Pen srPen = new Pen(Color.LightBlue, 0);
         //画噪点
        for (int i = 0; i < 100; i++)
         {
             srGraph.DrawRectangle(srPen, srRandom.Next(1, srBmp.Width - 2), srRandom.Next(1, srBmp.Height - 2), 1, 1);
         }
       //将字符串转化为字符数组
         char[] srchars = srs.ToCharArray();
         //封状文本
         StringFormat srFormat = new StringFormat(StringFormatFlags.NoClip);
         //设置文本垂直居中
         srFormat.Alignment = StringAlignment.Center;
         //设置文本水平居中
         srFormat.LineAlignment = StringAlignment.Center;
         //定义字体颜色
         Color[] srColors ={ Color.Black, Color.Red, Color.DarkBlue, Color.Blue, Color.Orange, Color.Brown, Color.DarkCyan, Color.Purple };
         //定义字体
         string[] srFonts ={ "Verdana", "Microsoft Sans Serif", "Comic Sans MS", "Arial", "宋体" };
         //循环画出每个字符
         for (int i = 0, j = srchars.Length; i < j; i++)
         {
             //定义字体 参数分别为字体样式 字体大小 字体字形
          
           Font srFont = new Font(srFonts[srRandom.Next(5)], 12, FontStyle.Regular);
            //填充图形
            Brush srBrush = new SolidBrush(srColors[srRandom.Next(7)]);
            //定义坐标
            Point srPoint = new Point(16, 16);
            //定义倾斜角度
            float srangle = srRandom.Next(-srseedangle, srseedangle);
           //倾斜
           srGraph.TranslateTransform(srPoint.X, srPoint.Y);
            srGraph.RotateTransform(srangle);
            //填充字符
            srGraph.DrawString(srchars[i].ToString(), srFont, srBrush, 1, 1, srFormat);
            //回归正常
            srGraph.RotateTransform(-srangle);
            srGraph.TranslateTransform(2, -srPoint.Y);
        }
       srGraph.Dispose();
       return srBmp;
    }

    public static object[] CreateRegionCode(int strlength)
    {

        string[] rBase = new string[10] { "0", "1", "2", "3", "4", "5", "6", "7", "8", "9"};
        Random rnd = new Random();
      

        //定义一个object数组用来

        object[] bytes = new object[strlength];
      

        for (int i = 0; i < strlength; i++)
        {
            int r1 = rnd.Next(0, 10);
            string str_r1 = rBase[r1].Trim();
            rnd = new Random(r1 * unchecked((int)DateTime.Now.Ticks + i));//更换随机数发生器的种子避免产生重复值

       //定义两个字节变量存储产生的随机数字区位码
           byte byte1 = Convert.ToByte(str_r1, 16);
        
          

           //将产生的一个汉字的字节数组放入object数组中
            bytes.SetValue(byte1,i);

        }

        return bytes;

    }