C# 产生验证码 利用背景图片绘制

 /// <summary>        /// 产生验证码方法        /// </summary>        /// <returns></returns>        public void VerificationCode()        {            int _verificationLength = 6;            int _width = 100, _height = 20;            SizeF _verificationTextSize;            string path = Server.MapPath("~/Skins/Commmon/Texture.jpg");//使用一张背景图            Bitmap _bitmap = new Bitmap(path);            TextureBrush _brush = new TextureBrush(_bitmap);            //获取验证码            string _verificationText = VerficationText(_verificationLength);            //储存验证码            Session["VerificationCode"] = _verificationText.ToUpper();            Font _font = new Font("Arial", 14, FontStyle.Bold);            Bitmap _image = new Bitmap(_width, _height);            Graphics _g = Graphics.FromImage(_image);            //清空背景色            _g.Clear(Color.White);            //绘制验证码            _verificationTextSize = _g.MeasureString(_verificationText, _font);            _g.DrawString(_verificationText, _font, _brush, (_width - _verificationTextSize.Width) / 2, (_height - _verificationTextSize.Height) / 2);            _image.Save(Response.OutputStream, System.Drawing.Imaging.ImageFormat.Jpeg);        }