ASP.Net生成验证码

using System;
using System.Web;
using System.Drawing;
using System.Drawing.Imaging;
using System.IO;
public partial class images_code : System.Web.UI.Page
{
protected void Page_Load(object sender, EventArgs e)
{
string chkCode = string.Empty;
//颜色列表，用于验证码、噪线、噪点
Color[] color ={ Color.Black, Color.Red, Color.Blue, Color.Green, Color.Orange,Color.Brown, Color.DarkBlue };
//字体列表，用于验证码
string[] font ={ "Times New Roman", "MS Mincho", "Book Antiqua", "Gungsuh","PMingLiU", "Impact" };
//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();
//生成验证码字符串
for (int i = 0; i < 4; i++)
{
chkCode += character[rnd.Next(character.Length)];
}
//保存验证码的Cookie
HttpCookie anycookie = new HttpCookie("validateCookie");
anycookie.Values.Add("ChkCode", chkCode);
HttpContext.Current.Response.Cookies["validateCookie"].Values["ChkCode"] = chkCode;
Bitmap bmp = new Bitmap(80,20);
Graphics g = Graphics.fromImage(bmp);
g.Clear(Color.White);
//画噪线
for (int i = 0; i < 3; i++)
{
int x1 = rnd.Next(80);
int y1 = rnd.Next(20);
int x2 = rnd.Next(80);
int y2 = rnd.Next(20);
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, 11);
Color clr = color[rnd.Next(color.Length)];
g.DrawString(chkCode.ToString(), ft, new SolidBrush(clr), (float)i * 20 + 6, (float)2);
}
//画噪点
for (int i = 0; i < 50; 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);
}
//清除该页输出缓存，设置该页无缓存
Response.Buffer = true;
Response.ExpiresAbsolute = System.DateTime.Now.AddMilliseconds(0);
Response.Expires = 0