常用的生成验证码程序 ，图片效果如下：
源程序如下：
using System;
using System.Drawing;
using System.Drawing.Imaging;
using System.Collections.Generic;
using System.Text;
using System.IO;
using System.Web;
///
///
/// ** asp.net(C#) 生成验证码 **
///
/// file: GenerateCheckCode.cs
///
/// Author: 周振兴 (Zxjay 飘遥)
///
/// Date: 07-04-10
///
/// http://www.cnblogs.com/zxjay
///
///
public class GenerateCheckCode
{
private static string chkCode;
public static MemoryStream GenCheckCode()
{
//颜色列表，用于验证码、噪线、噪点
Color[] color ={ Color.Tomato, Color.OrangeRed, Color.Olive, Color.Gold, Color.GreenYellow,
Color.Blue, Color.LawnGreen, Color.Lime, Color.MediumSpringGreen, Color.Aqua, Color.RoyalBlue, Color.MediumBlue,
Color.BlueViolet, Color.MediumOrchid, Color.Fuchsia, Color.DeepPink, Color.HotPink };
//字体列表，用于验证码
string[] font = { "Times New Roman", "MS Mincho", "Book Antiqua", "Gungsuh", "PMingLiU" };
//验证码的字符集，去掉了一些容易混淆的字符
char[] character ={ '2', '3', '4', '5', '6', '8', '9', 'A', 'B', 'C', 'D', 'E', 'F', 'G',
'H', 'J', 'K', 'L', 'M', 'N', 'P', 'R', 'S', 'T', 'W', 'X', 'Y' };
Random rnd = new Random();
chkCode = string.Empty;
//生成验证码字符串
for (int i = 0; i < 4; i++)
{
chkCode += character[rnd.Next(character.Length)];
}
HttpContext.Current.Session["checkcode"] = chkCode;
Bitmap bmp = new Bitmap(100, 40);
Graphics g = Graphics.FromImage(bmp);
g.Clear(Color.White);
//画噪线
for (int i = 0; i < 10; i++)
{
int x1 = rnd.Next(100);
int y1 = rnd.Next(40);
int x2 = rnd.Next(100);
int y2 = rnd.Next(40);
Color clr = color[rnd.Next(color.Length)];
g.DrawLine(new Pen(clr), x1, y1, x2, y2);
}
//画验证码字符串
for (int i = 0; i < chkCode.Length; i++)
{
string fnt = font[rnd.Next(font.Length)];
Font ft = new Font(fnt, 18);
Color clr = color[rnd.Next(color.Length)];
g.DrawString(chkCode[i].ToString(), ft, new SolidBrush(clr), (float)i * 20 + 8, (float)8);
}
//画噪点
for (int i = 0; i < 100; i++)
{
int x = rnd.Next(bmp.Width);
int y = rnd.Next(bmp.Height);
Color clr = color[rnd.Next(color.Length)];
bmp.SetPixel(x, y, clr);
}
//画边框
Color col = color[rnd.Next(color.Length)];
g.DrawLine(new Pen(color[rnd.Next(color.Length)]), 0, 0, bmp.Width - 1, 0);
g.DrawLine(new Pen(color[rnd.Next(color.Length)]), 0, 0, 0, bmp.Height - 1);
g.DrawLine(new Pen(color[rnd.Next(color.Length)]), bmp.Width - 1, 0, bmp.Width - 1, bmp.Height - 1);
g.DrawLine(new Pen(color[rnd.Next(color.Length)]), 0, bmp.Height - 1, bmp.Width - 1, bmp.Height - 1);
//清除该页输出缓存，设置该页无缓存
HttpContext.Current.Response.Buffer = true;
HttpContext.Current.Response.ExpiresAbsolute = System.DateTime.Now.AddMilliseconds(0);
HttpContext.Current.Response.Expires = 0;
HttpContext.Current.Response.CacheControl = "no-cache";
HttpContext.Current.Response.AddHeader("Pragma", "No-Cache");
HttpContext.Current.Response.Cache.SetCacheability(HttpCacheability.NoCache);
//将验证码图片写入内存流，并将其以 "image/Png" 格式输出
MemoryStream ms = new MemoryStream();
try
{
bmp.Save(ms, ImageFormat.Png);
HttpContext.Current.Response.ClearContent();
HttpContext.Current.Response.ContentType = "image/Png";
return ms;
}
catch (Exception)
{
return null;
}
finally
{
//显式释放资源
bmp.Dispose();
g.Dispose();
}
}
}
使用方法如下：
新建名为 GenerateCheckCode.aspx 的文件，文件的内容为：
<%@ Page Language="C#" %>
<% Response.BinaryWrite(GenerateCheckCode.GenCheckCode().ToArray());%>
在需要验证码的地方放置的代码为：
<a href="javascript:void(0);" onfocus="javascript:blur();"
onclick="document.getElementById('img1').src='Control/CheckCode.aspx?id='+
(new Date().getTime().toString(36));"><img id="img1"
style="float: left; margin-top: 1px; margin-left: 3px;" class="imgcode"
title="看不清，换一张！" src="Control/CheckCode.aspx" />
a>
以上js代码为的是实现验证码的刷新。
验证码输入框中的字符和 Session["checkcode"] 的值比较是否相同来确定验证是否通过。
本文作者:飘遥的Blog 来源:http://www.cnblogs.com/zxjay/
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