asp.net验证码生成类(参考)

lt;param name="validateNum">验证码</param>
  public void CreateValidateGraphic(Page containsPage,string validateNum)
  {
   Bitmap image=new Bitmap((int)Math.Ceiling(validateNum.Length*12.5),22);
   Graphics g=Graphics.FromImage(image);
   try
   {
    //生成随机生成器
    Random random=new Random();
    //清空图片背景色
    g.Clear(Color.White);
    //画图片的干扰线
    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);
     g.DrawLine(new Pen(Color.Silver),x1,y1,x2,y2);
    }
    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(validateNum,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,ImageFormat.Jpeg);
    //输出图片
    containsPage.Response.Clear();
    containsPage.Response.ContentType="image/jpeg";
    containsPage.Response.BinaryWrite(stream.ToArray());
   }
   finally
   {
    g.Dispose();
    image.Dispose();
   }
  }
  /// <summary>
  /// 得到验证码图片的长度
  /// </summary>
  /// <param name="validateNumLength">验证码的长度</param>
  /// <returns></returns>
  public static int GetImageWidth(int validateNumLength)
  {
   return (int)(validateNumLength*12.5);
  }
  /// <summary>
  /// 得到验证码的高度
  /// </summary>
  /// <returns></returns>
  public static double GetImageHeight()
  {
   return 22.5;
  }
 }
}