ASP.NET验证码生成与识别

  1 using System;
  2 using System.Collections.Generic;
  3 using System.Drawing;
  4 using System.Drawing.Drawing2D;
  5 using System.Text;
  6 using System.Web;
  7 using System.Web.SessionState;
  8 
  9 namespace 验证码的生成与识别
 10 {
 11     /// <summary>
 12     /// ValidCodeHandler 的摘要说明
 13     /// </summary>
 14     public class ValidCodeHandler : IHttpHandler,IRequiresSessionState
 15     {
 16 
 17         public void ProcessRequest(HttpContext context)
 18         {
 19             //设置输出流的MIME类型
 20             //context.Response.ContentType = "image/png";      
 21 
 22             string strValidCode = GetValidCode(5);                                                  // 产生5位随机字符
 23 
 24             //如果要使用context.Session，需要添加命名空间using System.Web.SessionState;，然后再继承IRequiresSessionState接口
 25             context.Session["ValidCode"] = strValidCode;                                            //将字符串保存到Session中，以便需要时进行验证
 26             
 27             Bitmap image = new Bitmap(120, 40);                                                     //定义宽120像素，高30像素的数据定义的图像对象
 28             Graphics g = Graphics.FromImage(image);                                                 //绘制图片
 29             try
 30             {
 31 
 32                 Random random = new Random();                                                       //生成随机对象
 33                 g.Clear(Color.White);                                                               //清除图片背景色
 34 
 35                 for (int i = 0; i < 25; i++)                                               // 随机产生图片的背景噪线
 36                 {
 37                     int x1 = random.Next(image.Width);
 38                     int x2 = random.Next(image.Width);
 39                     int y1 = random.Next(image.Height);
 40                     int y2 = random.Next(image.Height);
 41                     g.DrawLine(new Pen(Color.Silver), x1, y1, x2, y2);
 42                 }
 43 
 44                 Font font = new System.Drawing.Font("微软雅黑", 20, (System.Drawing.FontStyle.Bold));  //设置图片字体风格
 45                 LinearGradientBrush brush = new LinearGradientBrush(new Rectangle(0, 0, image.Width, image.Height), Color.Blue, Color.DarkRed, 3, true);//设置画笔类型
 46                 g.DrawString(strValidCode, font, brush, 5, 2);                            //绘制随机字符
 47 
 48 
 49                 g.DrawRectangle(new Pen(Color.Silver), 0, 0, image.Width - 1, image.Height - 1);    //绘制图片的前景噪点
 50                 
 51                 System.IO.MemoryStream ms = new System.IO.MemoryStream();                           //建立存储区为内存的流
 52                 image.Save(ms, System.Drawing.Imaging.ImageFormat.Png);                              //将图像对象储存为内存流
 53                 context.Response.ClearContent();                                                    //清除当前缓冲区流中的所有内容
 54 
 55                 context.Response.ContentType = "image/png";
 56                 //context.Response.ContentType = "image/Gif";                                         //设置输出流的MIME类型
 57                 context.Response.BinaryWrite(ms.ToArray());                                         //将内存流写入到输出流
 58             }
 59             finally
 60             {
 61                 g.Dispose();
 62                 image.Dispose();
 63             }
 64         }
 65 
 66         /// <summary>
 67         /// 生成随机字符串
 68         /// </summary>
 69         /// <param name="num">随机字符的个数</param>
 70         /// <returns>返回随机产生的字符串</returns>
 71         private string GetValidCode(int num)
 72         {
 73             //定义一个允许的字符组成的字符串
 74             string strRandomCode = "ABCD1EF2GH3IJ4KL5MN6P7QR8ST9UVWXYZ";                                //定义要随机抽取的字符串
 75             //char[] chaStr = strRandomCode.ToCharArray();                                                //将定义的字符串转成字符数组
 76             StringBuilder sbValidCode = new StringBuilder();                                            //定义StringBuilder对象用于存放验证码
 77             //随机数生成器，用于随机产生验证码中字符
 78             Random rnd = new Random();                                                                   //随机函数，随机抽取字符
 79             for (int i = 0; i < num; i++)
 80             {
 81                 //随机获取一个字符
 82                 char a = strRandomCode[rnd.Next(0, strRandomCode.Length)];
 83                 //
 84                 sbValidCode.Append(a);
 85                 //以strRandomCode的长度产生随机位置并截取该位置的字符添加到StringBuilder对象中
 86                 //sbValidCode.Append(strRandomCode.Substring(rnd.Next(0, strRandomCode.Length), 1));
 87             }
 88             return sbValidCode.ToString();
 89         }
 90 
 91 
 92 
 93         public bool IsReusable
 94         {
 95             get
 96             {
 97                 return false;
 98             }
 99         }
100     }
101 }