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,image.Width,image.Height),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),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();

    }