动态生成验证码-蒲公英云

动态生成验证码

动态生成验证码在很多地方可以用到，最近在学习牛腩视频的时候，正好看到了，就此简单总结一下。

为了简单方便，我们新建一个验证码测试的项目名为test，然后在项目中新建一个文件夹，在这个文件夹中添加一个“一般处理程序”页，命名为WaterMark.ashx ，效果如下：

WaterMark.ashx中的代码如下所示：

<%@ WebHandler Language="C#" Class="WaterMark" %>
using System;
using System.Web;
using System.Drawing;
using System.Drawing.Drawing2D;
using System.Web.SessionState;
public class WaterMark : IHttpHandler, IRequiresSessionState  // 要使用session必须实现该接口,记得要导入System.Web.SessionState命名空间
{
    public void ProcessRequest(HttpContext context)
    {
        string checkCode = GenCode(5);  // 产生5位随机字符
        context.Session["Code"] = checkCode; //将字符串保存到Session中，以便需要时进行验证
        System.Drawing.Bitmap image = new System.Drawing.Bitmap(70, 22);
        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
            int i;
            for (i = 0; i < 25; 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.Silver), 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
            g.DrawRectangle(new Pen(Color.Silver), 0, 0, image.Width - 1, image.Height - 1);
            System.IO.MemoryStream ms = new System.IO.MemoryStream();
            image.Save(ms, System.Drawing.Imaging.ImageFormat.Gif);
            context.Response.ClearContent();
            context.Response.ContentType = "image/Gif";
            context.Response.BinaryWrite(ms.ToArray());
        }
        finally
        {
            g.Dispose();
            image.Dispose();
        }
    }
    /// <summary>
    /// 产生随机字符串
    /// </summary>
    /// <param name="num">随机出几个字符</param>
    /// <returns>随机出的字符串</returns>
    private string GenCode(int num)
    {
        string str = "0123456789ABCDEFGHIJKLMNOPQRSTUVWXYZ";
        char[] chastr = str.ToCharArray();
        string code = "";
        Random rd = new Random();
        int i;
        for (i = 0; i < num; i++)
        {
            code += str.Substring(rd.Next(0, str.Length), 1);
        }
        return code;
    }
    public bool IsReusable
    {
        get
        {
            return false;
        }
    }
}

在Default.aspx中代码如下：

<%@ Page Language="C#" AutoEventWireup="true" CodeFile="Default.aspx.cs" Inherits="_Default" %>
<!DOCTYPE html>
<html xmlns="http://www.w3.org/1999/xhtml">
<head runat="server">
<meta http-equiv="Content-Type" content="text/html; charset=utf-8"/>
    <title>验证码实验</title>
    <script lang ="javascript" type ="text/javascript" >
        function changeCode() {
            var imgNode = document.getElementById("vimg");
            imgNode.src = "handler/WaterMark.ashx?t=" + (new Date()).valueOf();
        }
    </script>    
</head>
<body>
    <form id="form1" runat="server">
    <div>
        <%--<p>验证码1：<img src="handler/WaterMark.ashx" id="vimg" alt="" οnclick="changeCode()" /></p>--%>
        <p>验证码2：<asp:Image ID="vimg" runat="server" ImageUrl ="handler/WaterMark.ashx" οnclick="changeCode()" /></p>
    </div>
    </form>
</body>
</html>

当验证输入的验证码与当前验证码是否一致时，代码如下：

string code = txtCode.Text.Trim().ToUpper();  //用户输入的验证码
        string rightCode = Session["Code"].ToString();
        if (code != rightCode )
        {
            Page.ClientScript.RegisterStartupScript(Page.GetType(), "message", "<script language='javascript' defer>alert('验证码输入错误！');</script>");
            txtCode.Text = "";
            return;
        }