/************************************************************************/
/* 类名：无
* 功能：生成验证码图片
* 完成时间：2009-8-11
* 版本号：1.0
* 修改时间：
* 作者：eping
* E-Mail:eping@live.com
/************************************************************************/
using System;
using System.Data;
using System.Configuration;
using System.Web;
using System.Web.Security;
using System.Web.UI;
using System.Web.UI.WebControls;
using System.Web.UI.WebControls.WebParts;
using System.Web.UI.HtmlControls;

using System.Drawing;  //添加引用

public partial class _Default : System.Web.UI.Page
{
    protected void Page_Load(object sender, EventArgs e)
    {
        //调用自定义方法绘制验证码
        CreateCheckCodeImage(GenerateCheckCode());
    }

    private string GenerateCheckCode()
    {
        //创建整型型变量
        int number;
        //创建字符型变量
        char code;
        //创建字符串变量并初始化为空
        string checkCode = String.Empty;
        //创建Random对象
        Random random = new Random();
        //使用For循环生成4个数字
        for (int i = 0; i < 4; i++)
        {
            //生成一个随机数
            number = random.Next();
            //将数字转换成为字符型
           code = (char)(‘0‘ + (char)(number % 10));        

            checkCode += code.ToString();
        }
        //将生成的随机数添加到Cookies中
        Response.Cookies.Add(new HttpCookie("CheckCode", checkCode));
        //返回字符串
        return checkCode;
    }

    private void CreateCheckCodeImage(string checkCode)
    {
        //判断字符串不等于空和null
        if (checkCode == null || checkCode.Trim() == String.Empty)
            return;
       //创建一个位图对象
        System.Drawing.Bitmap image = new System.Drawing.Bitmap((int)Math.Ceiling((checkCode.Length * 12.5)), 22);
        //创建Graphics对象
        Graphics g = Graphics.FromImage(image);

        try
        {
            //生成随机生成器
            Random random = new Random();

            //清空图片背景色
            g.Clear(Color.White);

            //画图片的背景噪音线
            for (int i = 0; i < 2; i++)
            {
                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.Black), x1, y1, x2, y2);
            }

            Font font = new System.Drawing.Font("Arial", 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);

            //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()));
            }

            //画图片的边框线
            g.DrawRectangle(new Pen(Color.Silver), 0, 0, image.Width - 1, image.Height - 1);

            //将图片输出到页面上
            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();
        }
    }
}