How to adjust size of programatically created Bitmap to match text drawn on it?

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);
        }
    }
}

Update: I wound up creating the Bitmap larger than I would ever need, get the graphics from that bitmap and use the MeasureString method to get the size the text I am going to write and then crop that part of the bitmap into a new bitmap like so.

 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(500, 500))
    {
        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);
            System.Drawing.SizeF bmpSize = graph.MeasureString(text, fnt);
            System.Drawing.Rectangle rect = new System.Drawing.Rectangle(new System.Drawing.Point(0, 0), bmpSize.ToSize());
            System.Drawing.Bitmap croppedBmp = bmp.Clone(rect, bmp.PixelFormat);
            graph = System.Drawing.Graphics.FromImage(croppedBmp);
            graph.DrawString(text, fnt, brush开发者_如何学JAVA, new System.Drawing.Point(0, 0));
            string imgPath = System.IO.Path.Combine(@"C:\Development\MyPath\Images\Text", System.IO.Path.GetRandomFileName());
            croppedBmp.Save(imgPath);
            context.Response.WriteFile(imgPath);
        }
    }

I would guess there's a System.Drawing.Graphics.MeasureString method which will return the size of the specified text using the specified font.

Then, you may resize your image accordingly, or resize your text accordingly in order to make them both fit together.

Perhaps an eye out to this question and answers will guide you somehow, as the question is about sizing text so that it may fit within an area. You seem to wish to make something alike, so the algorithm may inspire you.