.net验证图片做法

private void ShowImg(string colorf,string colorb)    {        //colorf=FF0000&colorb=EFF3FF        Random ran = new Random();        int intRandom = ran.Next(10001, 99999);        //将随机数(验证字串)写入Session        Session.RemoveAll();        Session["RandCode"] = intRandom;        //字体名        string strFontName = "Arial";        //字体大小        int intFontSize = 9;        //图像宽        int intWidth = 40;        //图像长        int intHeight = 14;        //背景颜色        Color bgColor = ColorTranslator.FromHtml("#" + colorf);        //前景颜色        Color foreColor = ColorTranslator.FromHtml("#" + colorb);        //产生字体        Font forFont = new Font(strFontName, intFontSize, FontStyle.Bold);        //生成图片        Bitmap newBitmap = new Bitmap(intWidth, intHeight, PixelFormat.Format32bppArgb);        Graphics g = Graphics.FromImage(newBitmap);        //定义一个四方形框与字片一样大小        Rectangle newRect = new Rectangle(0, 0, intWidth, intHeight);        //涂上背景色        g.FillRectangle(new SolidBrush(bgColor), newRect);        //写字        g.DrawString(intRandom.ToString(), forFont, new SolidBrush(foreColor), 2, 2);        MemoryStream mStream = new MemoryStream();        //存入MemoryStream        string filename = @"F:/my/mp3/" + DateTime.Now.ToString().Replace("-","").Replace(":","").Replace(" ","")+".gif";        newBitmap.Save(filename, ImageFormat.Gif);        g.Dispose();        newBitmap.Dispose();        Image1.ImageUrl = filename;    }