网页验证码

 

using System;using System.Web;using System.Drawing;public partial class CheckCode : System.Web.UI.Page{    protected void Page_Load(object sender, EventArgs e)    {        this.CreateCheckCodeImage(GenerateCheckCode());    }    //产生验证码    private string GenerateCheckCode()    {        int number;//存放随机数        char code;//验证码字符        string checkCode = string.Empty;//验证码字符串        Random random = new Random();        for (int i = 0; i < 4; i++)        {            number = random.Next();            code = (char)('A' + (char)(number % 26));//产生26个大写字母            checkCode += code.ToString();        }        Session["CheckCode"] = checkCode;        return checkCode;    }    //产生验证码的前、背景图像    private void CreateCheckCodeImage(string checkCode)    {        if (checkCode == null || checkCode.Trim() == string.Empty)            return;        Bitmap image = new Bitmap(66, 23);        Graphics g = Graphics.FromImage(image);        try        {            Random random = new Random();//产生随机数            g.Clear(Color.White);//清空图片背景色            for (int i = 0; i < 25; i++)  //随机画25条干扰线            {                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, x2, y1, y2);            }            Font font = new Font("Times New Roman", 14, (FontStyle.Bold | FontStyle.Italic));//设置字体类型            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);//设置字体渐变效果            g.DrawString(checkCode, font, brush, 2, 2);//将验证码字符串填充到g中            //画图片的前景噪音点            for (int i = 0; i < 100; i++)            {                int x = random.Next(image.Width);                int y = random.Next(image.Height);                image.SetPixel(x, y, Color.FromArgb(random.Next()));//通过随机数产生坐标点和颜色            }            //画图片的边框线            g.DrawRectangle(new Pen(Color.Silver), 0, 0, image.Width - 1, image.Height - 1);            System.IO.MemoryStream ms = new System.IO.MemoryStream();//创建内存流            image.Save(ms, System.Drawing.Imaging.ImageFormat.Gif);//将图片以Gif格式保存到内存流中            HttpContext.Current.Response.ContentType = "image/gif";            HttpContext.Current.Response.BinaryWrite(ms.ToArray());        }        finally        {            g.Dispose();            image.Dispose();        }    }}