C#如何消除验证码图片的锯齿效果

string color = "#ff6633";     System.Drawing.Bitmap image = new System.Drawing.Bitmap(170, 35);    Graphics g = Graphics.FromImage(image);    try    {      g.TextRenderingHint= TextRenderingHint.AntiAlias; //消除锯齿            //生成随机生成器      Random random = new Random();     //清空图片背景色      //g.Clear(Color.Transparent);      //画图片的背景噪音线      /*for (int i = 0; i < 2; 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.Black), x1, y1, x2, y2);      }      */      System.Drawing.ColorConverter colConvert = new System.Drawing.ColorConverter();      Color fontColor =(System.Drawing.Color)colConvert.ConvertFromString(color);      Font font = new System.Drawing.Font("Arial", 18, System.Drawing.FontStyle.Bold);      LinearGradientBrush brush = new LinearGradientBrush(new Rectangle(0, 0, image.Width, image.Height), fontColor, fontColor,LinearGradientMode.Horizontal);      g.DrawString(phone, font, brush, 2, 2);      //画图片的前景噪音点       //for (int i = 0; i < 50; 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.White), 0, 0, image.Width - 1, image.Height - 1);       System.IO.MemoryStream ms = new System.IO.MemoryStream();      Color backColor = image.GetPixel(1, 1);      image.MakeTransparent(backColor);      image.Save(ms, System.Drawing.Imaging.ImageFormat.Png);      context.Response.ClearContent();      context.Response.ContentType = "image/x-png";      context.Response.BinaryWrite(ms.ToArray());    }    finally    {      g.Dispose();      image.Dispose();    }