ImageFromScrollView

MainPage.xaml

<Grid RowDefinitions="300,10,50,10,50" RowSpacing="0" Margin="0" Padding="0">
    <ScrollView x:Name="scroll"
            Margin="0" Padding="0">

        <StackLayout x:Name="stack"
                Margin="0" Padding="0" Spacing="0">
            <BoxView HeightRequest="200" Background="Violet"/>
            <BoxView HeightRequest="200" Background="Green"/>
            <BoxView HeightRequest="200" Background="Blue"/>
        </StackLayout>
    </ScrollView>

    <Button Grid.Row="2" Text="Capture ScrollView" Background="#990000ff" 
                Command="{Binding CaptureCommand}" CommandParameter="{x:Reference scroll}"/>

    <Button Grid.Row="4" Text="Capture StackLayout" Background="#990000ff" 
                Command="{Binding CaptureCommand}" CommandParameter="{x:Reference stack}"/>
</Grid>

MainViewModel.cs

public class MainViewModel : BaseNotifier
{
    public MainViewModel()
        => CaptureCommand = new Command<VisualElement>(OnCapture);

    public ICommand CaptureCommand { get; set; }

    async void OnCapture(VisualElement element)
    {
        try
        {
            using var stream = await element.CaptureImageAsync();

            var dir = FileSystem.CacheDirectory;
            var filepath = Path.Combine(dir, "image.jpg");

            if (File.Exists(filepath))
                File.Delete(filepath);

            using var fileStream = File.OpenWrite(filepath);
            stream.CopyTo(fileStream);
            fileStream.Close();

            await Share.RequestAsync(new ShareFileRequest(new ShareFile(filepath)));
        }
        catch (Exception ex)
        {

        }
    }
}