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();
            }
        }