中文验证码

   protected   void  Page_Load( object  sender, EventArgs e)
        {
             //  在此处放置用户代码以初始化页面
            Encoding gb  =  Encoding.GetEncoding( " gb2312 " );
             object [] bytes  =  CreateRegionCode( 4 ); // 调用函数产生4个随机中文汉字编码  
             // 根据汉字编码的字节数组解码出中文汉字
             string  str1  =  gb.GetString(( byte [])Convert.ChangeType(bytes[ 0 ],  typeof ( byte [])));
             string  str2  =  gb.GetString(( byte [])Convert.ChangeType(bytes[ 1 ],  typeof ( byte [])));
             string  str3  =  gb.GetString(( byte [])Convert.ChangeType(bytes[ 2 ],  typeof ( byte [])));
             string  str4  =  gb.GetString(( byte [])Convert.ChangeType(bytes[ 3 ],  typeof ( byte [])));
            Session[Config.Reg_ValidateChars]  =  str1  +  str2  +  str3  +  str4; // 用于与输入的验证码作对比
            CreateImage(str1  +  str2  +  str3  +  str4);
        }
         ///   <summary>
         ///  随机产生汉字
         ///   </summary>
         ///   <param name="strlength"></param>
         ///   <returns></returns>
         private   static   object [] CreateRegionCode( int  strlength)
        {
             string [] rBase  =   new  String[ 16 ] {  " 0 " ,  " 1 " ,  " 2 " ,  " 3 " ,  " 4 " ,  " 5 " ,  " 6 " ,  " 7 " ,  " 8 " ,  " 9 " ,  " a " ,  " b " ,  " c " ,  " d " ,  " e " ,  " f "  }; // 定义一个字符串数组储存汉字编码的组成元素
            Random rnd  =   new  Random();
             object [] bytes  =   new   object [strlength]; // 定义一个object数组用来
             for  ( int  i  =   0 ; i  <  strlength; i ++ )
            {
                 // 区位码第1位
                 int  r1  =  rnd.Next( 11 ,  14 );
                 string  str_r1  =  rBase[r1].Trim();
                 // 区位码第2位
                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
                 int  r2;
                 if  (r1  ==   13 )
                { r2  =  rnd.Next( 0 ,  7 ); }
                 else
                { r2  =  rnd.Next( 0 ,  16 ); }
                 string  str_r2  =  rBase[r2].Trim();
                 // 区位码第3位
                rnd  =   new  Random(r2  *   unchecked (( int )DateTime.Now.Ticks)  +  i);
                 int  r3  =  rnd.Next( 10 ,  16 );
                 string  str_r3  =  rBase[r3].Trim();
                 // 区位码第4位
                rnd  =   new  Random(r3  *   unchecked (( int )DateTime.Now.Ticks)  +  i);
                 int  r4;
                 if  (r3  ==   10 )
                { r4  =  rnd.Next( 1 ,  16 ); }
                 else   if  (r3  ==   15 )
                { r4  =  rnd.Next( 0 ,  15 ); }
                 else
                { r4  =  rnd.Next( 0 ,  16 ); }
                 string  str_r4  =  rBase[r4].Trim();
                 // 定义两个字节变量存储产生的随机汉字区位码
                 byte  byte1  =  Convert.ToByte(str_r1  +  str_r2,  16 );
                 byte  byte2  =  Convert.ToByte(str_r3  +  str_r4,  16 );
                 byte [] str_r  =   new   byte [] { byte1, byte2 }; // 将两个字节变量存储在字节数组中
                bytes.SetValue(str_r, i); // 将产生的一个汉字的字节数组放入object数组中
            }
             return  bytes;
        }
         ///   <summary>
         ///  生成中文验证码图片
         ///   </summary>
         ///   <param name="checkCode"></param>
         private   void  CreateImage( string  checkCode)
        {
             if  (checkCode  ==   null   ||  checkCode.Trim()  ==  String.Empty)
                 return ;
            System.Drawing.Bitmap image  =   new  System.Drawing.Bitmap(( int )Math.Ceiling((checkCode.Length  *   21.0 )),  22 );
            Graphics g  =  Graphics.FromImage(image);
             try
            {
                Random random  =   new  Random(); // 生成随机生成器
                g.Clear(Color.White); // 清空图片背景色
                 for  ( int  i  =   0 ; i  <   20 ; i ++ ) // 画图片的背景噪音线
                {
                     int  x1  =  random.Next(image.Width);
                     int  x2  =  random.Next(image.Width);
                     int  y1  =  random.Next(image.Height);
                     int  y2  =  random.Next(image.Height);
                    g.DrawLine( new  Pen(Color.Silver), x1, y1, x2, y2);
                }
                Font font  =   new  System.Drawing.Font( " 楷体 " ,  12 , (System.Drawing.FontStyle.Bold));
                System.Drawing.Drawing2D.LinearGradientBrush brush  =   new

            System.Drawing.Drawing2D.LinearGradientBrush( new  Rectangle( 0 ,  0 , image.Width, image.Height), Color.Blue, Color.DarkRed,  1.2f ,

             true );
                g.DrawString(checkCode, font, brush,  2 ,  2 );
                 for  ( int  i  =   0 ; i  <   100 ; i ++ ) // 画图片的前景噪音点
                {
                     int  x  =  random.Next(image.Width);
                     int  y  =  random.Next(image.Height);
                    image.SetPixel(x, y, Color.FromArgb(random.Next()));
                }
                g.DrawRectangle( new  Pen(Color.Silver),  0 ,  0 , image.Width  -   1 , image.Height  -   1 ); // 画图片的边框线
                System.IO.MemoryStream ms  =   new  System.IO.MemoryStream();
                image.Save(ms, System.Drawing.Imaging.ImageFormat.Gif);
                Response.ClearContent();
                Response.ContentType  =   " image/Gif " ;
                Response.BinaryWrite(ms.ToArray());
            }
             finally
            {
                g.Dispose();
                image.Dispose();
            }
        }