using System;

 using System.Collections.Generic;

 using System.Drawing;

 using System.Linq;

 using System.Web;

 namespace vcodeDemo

 {

     /// <summary>

     /// vcode 写法的说明

     /// </summary>

     public class c01vcode : IHttpHandler,System.Web.SessionState.IRequiresSessionState

     //如果要在一般处理程序中能够正常使用session则必须实现IRequiresSessionState接口

     {

         public void ProcessRequest(HttpContext context)

         {

             //1 设置ContentType为图片类型

             context.Response.ContentType = "image/jpeg";

             //2 准备要作画的图片对象,宽度为80 高度为25  ,Bitmap:位图

             using (Image img = new Bitmap(, ))

             {

                 // 从img对象上定义画家

                 using (Graphics g = Graphics.FromImage(img))

                 {

                     //以白色来清除位图的背景

                     g.Clear(Color.White);

                     //画图片的边框为红色,从左上角开始画满整个图片

                     g.DrawRectangle(Pens.Red, , , img.Width - , img.Height - );

                     //在验证码文字前面画50个噪点

                     this.DrawPoint(, g, img.Width, img.Height);

                     //得到验证码文本字符串(随机产生4个字符)

                     string vcode = this.GetVCode();

                     //保存验证码文本字符串到session中

                     context.Session["vcode"] = vcode;

                     //将验证码字符串写入到图片对象上

                     g.DrawString(vcode

                         , new Font("Arial", , FontStyle.Strikeout | FontStyle.Bold) // 给文本加中横线和加粗

                         , new SolidBrush(Color.Red)

                         , new PointF(r.Next(), r.Next())

                         );

                     //在验证码文字后面画50个噪点

                     this.DrawPoint(, g, img.Width, img.Height);

                 }

                 //将验证码输出给浏览器

                 img.Save(context.Response.OutputStream, System.Drawing.Imaging.ImageFormat.Jpeg);

             }

         }

         /// <summary>

         /// 在图片对象上画噪点

         /// </summary>

         /// <param name="count"></param>

         void DrawPoint(int count, Graphics g, int width, int height)

         {

             for (int i = ; i < count; i++)

             {

                 int x = r.Next(width);

                 int y = r.Next(height);

                 g.DrawLine(Pens.Blue

                     , new Point(x, y)

                     , new Point(x + , y + )

                     );

             }

         }

         /// <summary>

         /// 定义产生随机数的对象

         /// </summary>

         Random r = new Random();

         /// <summary>

         /// 产生验证码文本字符串

         /// </summary>

         /// <param name="count"></param>

         /// <returns></returns>

         string GetVCode(int count)

         {

             //声明返回值

             string rescode = "";

             string codestr = "ABCDabcd123456789";

             char[] codeArr = codestr.ToArray();

             for (int i = ; i < count; i++)

             {

                 rescode += codeArr[r.Next(codestr.Length)];

             }

             //返回字符串

             return rescode;

         }

         public bool IsReusable

         {

             get

             {

                 return false;

             }

         }

     }

 }