Storing SignaturePad Points in Database and rebuilding

Hi All,

I'm storing a signature (by serializing points) in a database and then attempting to recreate the signature... and it's not going to plan. A snippet of my code is below

Code Behind

            private async void SaveButton_Clicked(object sender, EventArgs e)
            {
            string points_string = JsonConvert.SerializeObject(PadView.Points.ToArray());

           // store to db, fetch

           Xamarin.Forms.Point[] points = JsonConvert.DeserializeObject<Xamarin.Forms.Point[]>(points_string);

           SignaturePadCanvasView sig = new SignaturePadCanvasView();

                sig.Points = pnts;

                // img is null at this point
                Stream img = await sig.GetImageStreamAsync(SignatureImageFormat.Png);


                // do something with the stream, in my case add to a padf
        }

XAML

<?xml version="1.0" encoding="utf-8" ?>
<ContentPage xmlns="http://xamarin.com/schemas/2014/forms"
            xmlns:x="http://schemas.microsoft.com/winfx/2009/xaml"
            xmlns:local="clr-namespace:H1PaperlessApp"
            xmlns:forms="clr-namespace:SignaturePad.Forms;assembly=SignaturePad.Forms"
            x:Class="H1PaperlessApp.Views.Temppage"
            Padding="10">

    <StackLayout>

        <forms:SignaturePadView x:Name="PadView"
                            HeightRequest="350"
                            WidthRequest="240"
                            BackgroundColor="White"
                            StrokeColor="Black"
                            StrokeWidth="2"/>

        <Button Text="Save" FontSize="30" BackgroundColor="DodgerBlue" TextColor="White"
            Clicked="SaveButton_Clicked"/>
    </StackLayout>
</ContentPage>

My problem is that GetImageStreamAsync is returning null and I can't work out why. Any suggestions?