ASP.NET 画图与图像处理－提供一个很好的验证码程序

protected void Page_Load(object sender, EventArgs e)
{
    BugNote.Common.CheckCode code = new BugNote.Common.CheckCode();
    code.CreateCheckCodeImage(this, BugNote.Common.CheckCode.GenerateCheckCode());
}

using System;
using System.Collections.Generic;
using System.Text;
using System.Drawing;
using System.Drawing.Imaging;
using System.Web.UI;
using System.Drawing.Drawing2D;
using System.IO;
   
   
namespace BugNote.Common
{
    ///     
    ///   功能描述:验证码基础类  
    ///     
    public class CheckCode
    {
        ///     
        ///   生成字符型验证码  
        ///     
        ///   字符型验证码(四位）  
        public static string GenerateCheckCode()
        {
            int number;
            char code;
            string checkCode = String.Empty;
   
            System.Random random = new Random();
   
            for (int i = 0; i < 4; i++)
            {
                number = random.Next();
   
                if (number % 2 == 0)
                    code = (char)('0' + (char)(number % 10));
                else
                    code = (char)('A' + (char)(number % 26));
   
                checkCode += code.ToString();
            }
            return checkCode;
            //throw   new   System.NotImplementedException();  
        }
        ///     
        ///   创建验证码的图片  
        ///   by   David   2006-12-28   16:10  
        ///     
        ///   要输出到的page对象  
        ///   验证码  
        public void CreateCheckCodeImage(Page containsPage, string checkCode)
        {
            System.Drawing.Bitmap image = new 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  
                g.Clear(Color.White);
                //画出图片的干扰线  
                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);
                }
                Font font = new Font("Arial", 12, (FontStyle.Bold | FontStyle.Italic));
                LinearGradientBrush brush = new LinearGradientBrush(new Rectangle(0, 0,
                        image.Width, image.Height),
                        Color.Blue, Color.DarkRed, 1.2f, true);
                g.DrawString(checkCode, font, brush, 3, 2);
                //画图片的前景干扰点  
                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);
                //保存图片数据  
                MemoryStream stream = new MemoryStream();
                image.Save(stream, System.Drawing.Imaging.ImageFormat.Gif);
                //输出图片containsPage  
                containsPage.Response.Clear();
                containsPage.Response.ContentType = "image/bmp";
                containsPage.Response.BinaryWrite(stream.ToArray());
   
            }
            finally
            {
                g.Dispose();
                image.Dispose();
            }
        }
   
   
        #region     得到验证码图片的长度
        ///     
        ///   得到验证码图片的长度  
        ///   by   David   2006-12-28   16:35  
        ///     
        ///   验证码的长度  
        ///     
        public static int GetImageWidth(int validateNumLength)
        {
            return (int)(validateNumLength * 12.5);
        }
        #endregion
   
   
        #region   得到验证码的高度
        ///     
        ///   得到验证码的高度  
        ///   by   David   2006-12-28   16:50  
        ///     
        ///     
        public static double GetImageHeight()
        {
            return 22.5;
        }
        #endregion
    }
}