createImageFromWidget function

Future<Uint8List> createImageFromWidget(BuildContext context, Widget widget, { double docWidth = _kDefaultWidth, double docHeight = _kDefaultHeight, })

Creates an image from the given widget.

The context parameter represents the build context. The widget parameter is the widget to create an image from. The docWidth parameter (optional) specifies the width of the document. Default is _kDefaultWidth. The docHeight parameter (optional) specifies the height of the document. Default is _kDefaultHeight.

Returns a Future that completes with a Uint8List containing the image data.

Implementation

Future<Uint8List> createImageFromWidget(
  BuildContext context,
  Widget widget, {
  double docWidth = _kDefaultWidth,
  double docHeight = _kDefaultHeight,
}) async {
  final RenderRepaintBoundary repaintBoundary = RenderRepaintBoundary();

  final BuildOwner buildOwner = BuildOwner(focusManager: FocusManager());

  final RenderObjectToWidgetElement<RenderBox> rootElement = RenderObjectToWidgetAdapter<RenderBox>(
    container: repaintBoundary,
    child: Directionality(
      textDirection: TextDirection.ltr,
      child: IntrinsicHeight(
        child: IntrinsicWidth(
          child: Container(
            color: Colors.white,
            child: widget,
          ),
        ),
      ),
    ),
  ).attachToRenderTree(buildOwner);

  buildOwner
    ..buildScope(rootElement)
    ..finalizeTree();

  ui.FlutterView view = View.of(context);

  final RenderView renderView = RenderView(
    view: view,
    child: RenderPositionedBox(
      alignment: Alignment.center,
      child: repaintBoundary,
    ),
    configuration: ViewConfiguration(
      size: Size(docWidth, docHeight),
      devicePixelRatio: view.devicePixelRatio,
    ),
  );

  final PipelineOwner pipelineOwner = PipelineOwner()..rootNode = renderView;
  renderView.prepareInitialFrame();

  pipelineOwner
    ..flushLayout()
    ..flushCompositingBits()
    ..flushPaint();

  ui.Image image = await repaintBoundary.toImage(pixelRatio: view.devicePixelRatio);
  ByteData? byteData = await image.toByteData(format: ui.ImageByteFormat.png);

  Uint8List? result = byteData?.buffer.asUint8List();

  return result!;
}