How do I get get X & Y screen coordinates from a GMAP.net Marker in C#?

Question

I am writing an application in C# and I need to get the X & Y screen coordinates from a marker inside the GMAP.net map control so I can plot an overlay above the control. The overlay is for generating a heatmap (the overlay is a transparent picturebox).

Here is what I have so far but it is not doing anything useful.

        private void generateBitmap(List<GMapMarker> markers)
        {
            HeatPoints.Clear();

            foreach (GMapMarker m in markers)
            {
                GPoint px = gMapControl1.MapProvider.Projection.FromLatLngToPixel(m.Position, (int)gMapControl1.Zoom); // I was expecting this to give me xy screen coords
                HeatPoints.Add(new HeatPoint((int)px.X, (int)px.Y, eventIntensity(JsonConvert.DeserializeObject<WalkSafe.ReportEvent>(m.Tag.ToString()))));
            }

            Bitmap map = new Bitmap(heatImage.Width, heatImage.Height);
            heatImage.Image = heatlib.CreateIntensityMask(map, HeatPoints);
        }

Any help would be greatly appreciated :)