生成图片验证码的工具类

页面的调用代码：

跟JSP中的一样，在image这个地方放的是一个SERVLET

<asp:Image ID="Image1" runat="server" Height="22px"
??????????????????????? ImageUrl="~/ValidateNum.aspx" Width="58px" />

?

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;//引入命名空间

public partial class ValidateNum : System.Web.UI.Page
{
??? protected void Page_Load(object sender, EventArgs e)
??? {
??????? if(!this.IsPostBack)
??????? {
??????????? string validateNum = this.CreateRandomNum(4);
??????????? CreateImage(validateNum);
??????????? Session["ValidateNum"] = validateNum;
??????? }
??? }
??? //生成随机字符串
??? private string CreateRandomNum(int NumCount)
??? {
??????? string allChar = "0,1,2,3,4,5,6,7,8,9,A,B,C,D,E,F,G,H,I,J,K,L,M,N,O,P,Q,R,S,T,U,W,X,Y,Z";
??????? string[] allCharArray = allChar.Split(',');//拆分成数组
??????? string randomNum = "";
??????? int temp = -1;//记录上次随机数的数值，尽量避免产生几个相同的随机数

??????? Random rand = new Random();
??????? for (int i = 0; i < NumCount; i++)
??????? {
??????????? if (temp != -1)
??????????? {
??????????????? rand = new Random(i * temp * ((int)DateTime.Now.Ticks));
??????????? }
??????????? int t = rand.Next(35);
??????????? if (temp == t)
??????????? {
??????????????? return CreateRandomNum(NumCount);
??????????? }
??????????? temp = t;
??????????? randomNum += allCharArray[t];
??????? }
??????? return randomNum;
??? }
??? //生成图片
??? private void CreateImage(string validateNum)
??? {
??????? if (validateNum == null || validateNum.Trim() == String.Empty)
??????????? return;
??????? //生成Bitmap图像
??????? System.Drawing.Bitmap image = new System.Drawing.Bitmap(validateNum.Length * 12 + 10, 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(validateNum, 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();
??????????? //将图像保存到指定的流
??????????? image.Save(ms, System.Drawing.Imaging.ImageFormat.Gif);
??????????? Response.ClearContent();
??????????? Response.ContentType = "image/Gif";
??????????? Response.BinaryWrite(ms.ToArray());
??????? }
??????? finally
??????? {
??????????? g.Dispose();
??????????? image.Dispose();
??????? }
??? }
}