How to Take screenshot of widget in Flutter web

I am trying to take a screenshot of a specific widget in Flutter (website development) but I am getting an exception:

'HtmlImage' can't be converted using toByteData

Is there any way to resolve the issue or take the screenshot in another way?

This method worked when I developed an android app.

Future<String> saveScreenshot(BuildContext context) async
  {
    // Get image
    ui.Image renderedImage = await writeKey.currentState.rendered;
    setState(() {image = renderedImage;});

    // Encode image
    ByteData byteData = image.buffer.toByteData(format: ui.ImageByteFormat.png); //Not working
    var pngBytes =  byteData.buffer.asUint8List();

    // Create strings for message
    String bs64 = base64Encode(pngBytes);
    String size = bs64.length.toString();

    // send image to server and get answer from it
    var ans = await Network.communicate(bs64, size, context);
    return ans;
  }