Xamarin Barcode ZXingBarcodeImageView .. how to set full width available ?

I'm using ZXingBarcodeImageView.... following is my code - the bar code is not using full width available. I'm not sure why ... any help is appreciated...

 <ContentPage.Content>
    <StackLayout Orientation="Vertical" >
        <zxing:ZXingBarcodeImageView x:Name="BarCodeId" 
            BarcodeFormat="CODE_128"
            HorizontalOptions="FillAndExpand"  VerticalOptions="StartAndExpand"                                 BarcodeValue="12345"
            HeightRequest="150" MinimumHeightRequest="150" InputTransparent="True" >
            <zxing:ZXingBarcodeImageView.BarcodeOptions>
                <zxcm:EncodingOptions  Height="150" PureBarcode="True" />
            </zxing:ZXingBarcodeImageView.BarcodeOptions>
        </zxing:ZXingBarcodeImageView>
    </StackLayout>
</ContentPage.Content>