登录时候的图片验证码的实现
前台CheckCode.aspx
<%@ Page language="c#" Inherits="Guestbook.CheckCode" CodeFile="CheckCode.aspx.cs" %>
<!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.0 Transitional//EN" >
<HTML>
<HEAD>
<title>CheckCode</title>
<meta name="GENERATOR" Content="Microsoft Visual Studio .NET 7.1">
<meta name="CODE_LANGUAGE" Content="C#">
<meta name="vs_defaultClientScript" content="JavaScript">
<meta name="vs_targetSchema" content="http://schemas.microsoft.com/intellisense/ie5">
</HEAD>
<body>
<form id="Form1" method="post" runat="server">
<FONT face="宋体"></FONT>
</form>
</body>
</HTML>
![](http://images.csdn.net/syntaxhighlighting/OutliningIndicators/None.gif)
后台CheckCode.aspx.cs
using System;
using System.Collections;
using System.ComponentModel;
using System.Data;
using System.Drawing;
using System.Web;
using System.Web.SessionState;
using System.Web.UI;
using System.Web.UI.WebControls;
using System.Web.UI.HtmlControls;
![](http://images.csdn.net/syntaxhighlighting/OutliningIndicators/None.gif)
![](http://images.csdn.net/syntaxhighlighting/OutliningIndicators/None.gif)
![](http://images.csdn.net/syntaxhighlighting/OutliningIndicators/None.gif)
namespace Guestbook
![](http://images.csdn.net/syntaxhighlighting/OutliningIndicators/ExpandedBlockStart.gif)
...{
![](http://images.csdn.net/syntaxhighlighting/OutliningIndicators/ExpandedSubBlockStart.gif)
/**//// <summary>
/// 页面检查生成的Session["CheckCode"]
/// </summary>
public partial class CheckCode : System.Web.UI.Page
![](http://images.csdn.net/syntaxhighlighting/OutliningIndicators/ExpandedSubBlockStart.gif)
...{
![](http://images.csdn.net/syntaxhighlighting/OutliningIndicators/InBlock.gif)
protected void Page_Load(object sender, System.EventArgs e)
![](http://images.csdn.net/syntaxhighlighting/OutliningIndicators/ExpandedSubBlockStart.gif)
...{
this.CreateCheckCodeImage(GenerateCheckCode());
}
![](http://images.csdn.net/syntaxhighlighting/OutliningIndicators/InBlock.gif)
private string GenerateCheckCode()
![](http://images.csdn.net/syntaxhighlighting/OutliningIndicators/ExpandedSubBlockStart.gif)
...{
int number;
char code;
string checkCode = String.Empty;
![](http://images.csdn.net/syntaxhighlighting/OutliningIndicators/InBlock.gif)
System.Random random = new Random();
![](http://images.csdn.net/syntaxhighlighting/OutliningIndicators/InBlock.gif)
for(int i=0; i<5; i++)
![](http://images.csdn.net/syntaxhighlighting/OutliningIndicators/ExpandedSubBlockStart.gif)
...{
number = random.Next();
![](http://images.csdn.net/syntaxhighlighting/OutliningIndicators/InBlock.gif)
if(number % 2 == 0)
code = (char)('0' + (char)(number % 10));
else
code = (char)('A' + (char)(number % 26));
![](http://images.csdn.net/syntaxhighlighting/OutliningIndicators/InBlock.gif)
checkCode += code.ToString();
}
![](http://images.csdn.net/syntaxhighlighting/OutliningIndicators/InBlock.gif)
//Response.Cookies.Add(new HttpCookie("CheckCode", checkCode));
Session["CheckCode"]=checkCode;
return checkCode;
}
![](http://images.csdn.net/syntaxhighlighting/OutliningIndicators/InBlock.gif)
private void CreateCheckCodeImage(string checkCode)
![](http://images.csdn.net/syntaxhighlighting/OutliningIndicators/ExpandedSubBlockStart.gif)
...{
if(checkCode == null || checkCode.Trim() == String.Empty)
return;
![](http://images.csdn.net/syntaxhighlighting/OutliningIndicators/InBlock.gif)
System.Drawing.Bitmap image = new System.Drawing.Bitmap((int)Math.Ceiling((checkCode.Length * 12.5)), 22);
Graphics g = Graphics.FromImage(image);
![](http://images.csdn.net/syntaxhighlighting/OutliningIndicators/InBlock.gif)
try
![](http://images.csdn.net/syntaxhighlighting/OutliningIndicators/ExpandedSubBlockStart.gif)
...{
//生成随机生成器
Random random = new Random();
![](http://images.csdn.net/syntaxhighlighting/OutliningIndicators/InBlock.gif)
//清空图片背景色
g.Clear(Color.White);
![](http://images.csdn.net/syntaxhighlighting/OutliningIndicators/InBlock.gif)
//画图片的背景噪音线
for(int i=0; i<25; i++)
![](http://images.csdn.net/syntaxhighlighting/OutliningIndicators/ExpandedSubBlockStart.gif)
...{
int x1 = random.Next(image.Width);
int x2 = random.Next(image.Width);
int y1 = random.Next(image.Height);
int y2 = random.Next(image.Height);
![](http://images.csdn.net/syntaxhighlighting/OutliningIndicators/InBlock.gif)
g.DrawLine(new Pen(Color.Silver), x1, y1, x2, y2);
}
![](http://images.csdn.net/syntaxhighlighting/OutliningIndicators/InBlock.gif)
Font font = new System.Drawing.Font("Arial", 12, (System.Drawing.FontStyle.Bold | System.Drawing.FontStyle.Italic));
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);
![](http://images.csdn.net/syntaxhighlighting/OutliningIndicators/InBlock.gif)
//画图片的前景噪音点
for(int i=0; i<100; i++)
![](http://images.csdn.net/syntaxhighlighting/OutliningIndicators/ExpandedSubBlockStart.gif)
...{
int x = random.Next(image.Width);
int y = random.Next(image.Height);
![](http://images.csdn.net/syntaxhighlighting/OutliningIndicators/InBlock.gif)
image.SetPixel(x, y, Color.FromArgb(random.Next()));
}
![](http://images.csdn.net/syntaxhighlighting/OutliningIndicators/InBlock.gif)
//画图片的边框线
g.DrawRectangle(new Pen(Color.Silver), 0, 0, image.Width - 1, image.Height - 1);
![](http://images.csdn.net/syntaxhighlighting/OutliningIndicators/InBlock.gif)
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
![](http://images.csdn.net/syntaxhighlighting/OutliningIndicators/ExpandedSubBlockStart.gif)
...{
g.Dispose();
image.Dispose();
}
}
![](http://images.csdn.net/syntaxhighlighting/OutliningIndicators/InBlock.gif)
![](http://images.csdn.net/syntaxhighlighting/OutliningIndicators/InBlock.gif)
}
}
![](http://images.csdn.net/syntaxhighlighting/OutliningIndicators/None.gif)
-----------------------------------
调用页面Default.aspx
<tr>
<td align="center" height="30" >验证码</td>
<td style="height: 30px"><input name="Txt_imgCode" type="text" id="Txt_imgCode" size="5" maxlength="5" tabindex="3"/>
<img id="CodeImg" onclick="this.src='CheckCode.aspx'" src="CheckCode.aspx" />
<input onclick="document.getElementById('CodeImg').src='CheckCode.aspx?tmp='+Math.random()"
type="button" value="验证码" name="Btn_Re" /></td>
</tr>
之后在后台对Session["CheckCode"].ToString().ToLower()进行验证就行了,来判断验证码是否正确。