Flutter qrImage convert to Image

I'm using qr_flutter to create QrImage. It's ok but I would like to convert QrImage into image in order to create a PDF file to print on the printer. Please kindly help!

QrImage(
  data: qrString,
  size: 300.0,
  version: 10,
  backgroundColor: Colors.white,
),

Use a RepaintBoundary widget with a key to export the widget to a a b64 string which then you can export as an image.

Example:

Future<Uint8List> _getWidgetImage() async {
 try {
   RenderRepaintBoundary boundary =
      _renderObjectKey.currentContext.findRenderObject();
   ui.Image image = await boundary.toImage(pixelRatio: 3.0);
   ByteData byteData =
      await image.toByteData(format: ui.ImageByteFormat.png);
   var pngBytes = byteData.buffer.asUint8List();
   var bs64 = base64Encode(pngBytes);
   debugPrint(bs64.length.toString());
   return pngBytes;
 } catch (exception) {}

}

@override
Widget build(BuildContext context) {
    return Scaffold(
        body: Column(children: [
          RepaintBoundary(
            key: _renderObjectKey,
            child: QrImage(
            data: "some text",
            size: 300.0,
            version: 10,
            backgroundColor: Colors.white,
         ),
       ),
       RaisedButton(onPressed: () {
         _getWidgetImage();
       })
     ]));

}