【C#工具类】C#生成加减法验证码
开发出去的页面经常被别人以抓取的方式访问，造成服务器压力过大，IIS崩溃。这时候可以在经常被抓取的连接上添加验证码认证，可以有效的减轻服务器压力。
1.验证码输入页面
js：
function ValidateInput() {
var Num = document.getElementById("txtNum").value;
if (Num == "" || Num == str) {
alert("请输入验证码！");
return false;
}
return true;
}页面：
<img src="ValidCode.aspx" alt="验证码"/> <asp:TextBox ID="txtNum" runat="server" Width="40px">asp:TextBox>
<asp:Button ID="btnContinue" runat="server" Text="查询" ToolTip="查询信息" OnClick="btnContinue_Click"
OnClientClick="return ValidateInput();" />这里IMG是一个页面生成的，这个页面也是重点。最后说，现在看验证。
2.后台验证
protected void btnContinue_Click(object sender, EventArgs e)
{
try
{
if (txtNum.Text == Session["ValidCode"].ToString())
{
//.....Other Operation
}
else
{
RaiseAlert("验证码错误！");
}
txtNum.Text = "";
}
catch (Exception ex)
{
lblMsg.Text = ex.Message;
}3.验证码生成：
1）.页面：（就是一个正常的页面。）
<%@ Page Language="C#" AutoEventWireup="true" CodeFile="ValidCode.aspx.cs" Inherits="Admin_ValidCode" %>
<html xmlns="http://www.w3.org/1999/xhtml" >
<head runat="server">
<title>无标题页title>
head>
<body>
<form id="form1" runat="server">
<div>
div>
form>
body>
html>
2）后台生成：
using System;
using System.Data;
using System.Configuration;
using System.Collections;
using System.Web;
using System.Web.Security;
using System.Web.UI;
using System.Web.UI.WebControls;
using System.Web.UI.WebControls.WebParts;
using System.Web.UI.HtmlControls;
using System.Drawing;
//from http://i.aspx1.com
public partial class Admin_ValidCode : System.Web.UI.Page
{
protected void Page_Load(object sender, EventArgs e)
{
this.CreateCheckCodeImage(GenerateCheckCode());
}
private string GenerateCheckCode()
{
int intFirst, intSec, intTemp;
string checkCode = String.Empty;
System.Random random = new Random();
intFirst = random.Next(1, 10);
intSec = random.Next(1, 10);
switch (random.Next(1, 3).ToString())
{
case "2":
if (intFirst < intSec)
{
intTemp = intFirst;
intFirst = intSec;
intSec = intTemp;
}
checkCode = intFirst + "-" + intSec + "=";
Session["ValidCode"] = intFirst - intSec;
break;
default:
checkCode = intFirst + "+" + intSec + "=";
Session["ValidCode"] = intFirst + intSec;
break;
}
//Response.Cookies.Add(new HttpCookie("ValidCode",Movie.Common.AES.EncryptAes(checkCode)));
return checkCode;
}
#region 产生波形滤镜效果
private const double PI = 3.1415926535897932384626433832795;
private const double PI2 = 6.283185307179586476925286766559;
private System.Drawing.Bitmap TwistImage(Bitmap srcBmp, bool bXDir, double dMultValue, double dPhase)
{
System.Drawing.Bitmap destBmp = new Bitmap(srcBmp.Width, srcBmp.Height);
// 将位图背景填充为白色
System.Drawing.Graphics graph = System.Drawing.Graphics.FromImage(destBmp);
graph.FillRectangle(new SolidBrush(System.Drawing.Color.White), 0, 0, destBmp.Width, destBmp.Height);
graph.Dispose();
double dBaseAxisLen = bXDir ? (double)destBmp.Height : (double)destBmp.Width;
for (int i = 0; i < destBmp.Width; i++)
{
for (int j = 0; j < destBmp.Height; j++)
{
double dx = 0;
dx = bXDir ? (PI2 * (double)j) / dBaseAxisLen : (PI2 * (double)i) / dBaseAxisLen;
dx += dPhase;
double dy = Math.Sin(dx);
// 取得当前点的颜色
int nOldX = 0, nOldY = 0;
nOldX = bXDir ? i + (int)(dy * dMultValue) : i;
nOldY = bXDir ? j : j + (int)(dy * dMultValue);
System.Drawing.Color color = srcBmp.GetPixel(i, j);
if (nOldX >= 0 && nOldX < destBmp.Width
&& nOldY >= 0 && nOldY < destBmp.Height)
{
destBmp.SetPixel(nOldX, nOldY, color);
}
}
}
return destBmp;
}
#endregion
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 * 15.0)), 25);
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 < 12; 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", 16, (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, 1, 1);
//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()));
//}
//image = TwistImage(image, true, 3, 1);//画图片的波形滤镜效果
//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();
}
}
}