I have the following .ashx page that takes some query string parameters and returns a bitmap with the specified text written on it. The problem I have is that I am currently just manually setting the initial size of the bitmap at 100 X 100 when what I really want is to have the bitmap be just big enough to include all the text that was written to it. How can I do this?

  public void ProcessRequest (HttpContext context) {
    context.Response.ContentType = "image/png";
      string text = context.Request.QueryString["Text"];
    //set FontName
    string fontName;
    if (context.Request.QueryString["FontName"] != null)
    {
        fontName = context.Request.QueryString["FontName"];
    }
    else
    {
        fontName = "Arial";
    }
    //Set FontSize
    int fontEms;
    if (context.Request.QueryString["FontSize"] != null)
    {
        string fontSize = context.Request.QueryString["FontSize"];
        fontEms = Int32.Parse(fontSize);

    }
    else
    {
        fontEms = 12;
    }

    //Set Font Color
    System.Drawing.Color color;
    if (context.Request.QueryString["FontColor"] != null)
    {
        string fontColor = context.Request.QueryString["FontColor"];
        color = System.Drawing.ColorTranslator.FromHtml(fontColor);
        context.Response.Write(color.ToString());
    }
    else
    {
        color = System.Drawing.Color.Red;
    }
    using (System.Drawing.Text.PrivateFontCollection fnts = new System.Drawing.Text.PrivateFontCollection())
    using (System.Drawing.FontFamily fntfam = new System.Drawing.FontFamily(fontName))
    using (System.Drawing.SolidBrush brush = new System.Drawing.SolidBrush(color))
    using (System.Drawing.Bitmap bmp = new System.Drawing.Bitmap(100, 100))
    {
        using (System.Drawing.Font fnt = new System.Drawing.Font(fntfam, fontEms))
        {
            fnts.AddFontFile(System.IO.Path.Combine(@"C:\Development\Fonts\", fontName));
            System.Drawing.Graphics graph = System.Drawing.Graphics.FromImage(bmp);
            graph.DrawString(text, fnt, brush, new System.Drawing.Point(0, 0));
            string imgPath = System.IO.Path.Combine(@"C:\Development\MyPath\Images\Text", System.IO.Path.GetRandomFileName());
            bmp.Save(imgPath);
            context.Response.WriteFile(imgPath);
        }
    }
}