ImageFromXamarinUI - produces blank file

I have a Xamarin.Forms / Android app that displays graphics in an OpenGLView.I'm trying to use the NuGet "ImageFromXamarinUI" to capture an instantaneous screenshot of the graphics at a point in time, and save it to a file.

My "capture" code currently looks like:

        Stream imageStream = await myPage.myOpenGLView.CaptureImageAsync();        string myCaptureFilename = $"MLM - {ParamsEqSetName} - {System.DateTime.Now.ToString("yyyy_MM_d_HH_mm")}";        using (Stream stream = File.Open($"/storage/emulated/0/Pictures/{myCaptureFilename}", FileMode.Create))        {            imageStream.CopyTo(stream);            stream.Close();            stream.Dispose();        }

The file is being created successfully. But, when I try to open it as an image with the Photos app, I get a blank, black screen.

I expect to see the graphics that were being displayed at the moment that I executed the capture code. Instead, I get a blank, black screen.