namespace WebSiteNew{    public partial class CreateImg : System.Web.UI.Page    {        /// <summary>        /// 生成随即验证码        /// Create  by  高兴        /// 6、28  PM        /// </summary>        Random ran = new Random();        protected void Page_Load(object sender, EventArgs e)        {            string str = getRandomValidate(4);            Response.Cookies.Add(new HttpCookie("CheckCode", str));// 使用Cookies取验证码的值 = str; //这一步是为了将验证码写入Session，进行验证，不能缺省，也可一使用cookie            getImageValidate(str);        }        //得到随机字符串,长度自己定义        /// <summary>        /// Create  by  高兴        /// 6、28  PM        /// </summary>        /// <param name="len"></param>        /// <returns></returns>        private string getRandomValidate(int len)        {            int num;            int tem;            string rtuStr = "";            for (int i = 0; i < len; i++)            {                num = ran.Next();                /*                 * 这里可以选择生成字符和数字组合的验证码                 */                tem = num % 10 + ‘0‘;//生成数字                //tem = num % 26 + ‘A‘;//生成字符                rtuStr += Convert.ToChar(tem).ToString();            }            return rtuStr;        }        //生成图像        /// <summary>        /// Create  by  高兴        /// 6、28  PM        /// </summary>        /// <param name="strValue"></param>        private void getImageValidate(string strValue)        {            //string str = "OO00"; //前两个为字母O，后两个为数字0            int width = Convert.ToInt32(strValue.Length * 12);    //计算图像宽度            Bitmap img = new Bitmap(width, 23);            Graphics gfc = Graphics.FromImage(img);           //产生Graphics对象，进行画图            gfc.Clear(Color.White);            drawLine(gfc, img);            //写验证码，需要定义Font            Font font = new Font("arial", 12, FontStyle.Bold);            System.Drawing.Drawing2D.LinearGradientBrush brush =                new System.Drawing.Drawing2D.LinearGradientBrush(new Rectangle(0, 0, img.Width, img.Height), Color.DarkOrchid, Color.Blue, 1.5f, true);            gfc.DrawString(strValue, font, brush, 3, 2);            drawPoint(img);            gfc.DrawRectangle(new Pen(Color.DarkBlue), 0, 0, img.Width - 1, img.Height - 1);            //将图像添加到页面            MemoryStream ms = new MemoryStream();            img.Save(ms, System.Drawing.Imaging.ImageFormat.Gif);            //更改Http头            Response.ClearContent();            Response.ContentType = "image/gif";            Response.BinaryWrite(ms.ToArray());            //Dispose            gfc.Dispose();            img.Dispose();            Response.End();        }        /// <summary>        /// Create  by  高兴        /// 6、28  PM        /// </summary>        /// <param name="gfc"></param>        /// <param name="img"></param>        private void drawLine(Graphics gfc, Bitmap img)        {            //选择画10条线,也可以增加，也可以不要线，只要随机杂点即可            for (int i = 0; i < 10; i++)            {                int x1 = ran.Next(img.Width);                int y1 = ran.Next(img.Height);                int x2 = ran.Next(img.Width);                int y2 = ran.Next(img.Height);                gfc.DrawLine(new Pen(Color.Silver), x1, y1, x2, y2);      //注意画笔一定要浅颜色，否则验证码看不清楚            }        }        /// <summary>        /// Create  by  高兴        /// 6、28  PM        /// </summary>        /// <param name="img"></param>        private void drawPoint(Bitmap img)        {            /*            //选择画100个点,可以根据实际情况改变            for (int i = 0; i < 100; i++)            {                int x = ran.Next(img.Width);                int y = ran.Next(img.Height);                img.SetPixel(x,y,Color.FromArgb(ran.Next()));//杂点颜色随机            }             */            int col = ran.Next();//在一次的图片中杂店颜色相同            for (int i = 0; i < 100; i++)            {                int x = ran.Next(img.Width);                int y = ran.Next(img.Height);                img.SetPixel(x, y, Color.FromArgb(col));            }        }    }}

   function imgSrc() {            document.getElementById("GetImage").src = http://www.mamicode.com/"User/CreateImg.aspx?rand=lrand" + ‘&‘ + Math.random();        } <img id="GetImage" src=http://www.mamicode.com/"CreateImg.aspx" onclick="imgSrc()" />