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>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;namespace Guestbook
{
/// <summary>
/// 页面检查生成的Session["CheckCode"]
/// </summary> public partial class CheckCode : System.Web.UI.Page { protected void Page_Load(object sender, System.EventArgs e) { this.CreateCheckCodeImage(GenerateCheckCode()); } private string GenerateCheckCode() { int number; char code; string checkCode = String.Empty; System.Random random = new Random(); for(int i=0; i<5; i++) { number = random.Next(); if(number % 2 == 0) code = (char)('0' + (char)(number % 10)); else code = (char)('A' + (char)(number % 26)); checkCode += code.ToString(); } //Response.Cookies.Add(new HttpCookie("CheckCode", checkCode)); Session["CheckCode"]=checkCode; return checkCode; } private void CreateCheckCodeImage(string checkCode) { if(checkCode == null || checkCode.Trim() == String.Empty) return; System.Drawing.Bitmap image = new System.Drawing.Bitmap((int)Math.Ceiling((checkCode.Length * 12.5)), 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 for(int 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.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); //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); 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(); } } }
}-----------------------------------
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。