高德地图flutter sdk制作标记点的maker，对于移动端不支持size和颜色变更，顾采用传递自制的uint8list来实现。
Future<Uint8List> createImageFromWidget(Widget widget,
{Duration? wait, required Size imageSize}) async {
final RenderRepaintBoundary repaintBoundary = RenderRepaintBoundary();
final RenderView renderView = RenderView(
window: ui.window,
child: RenderPositionedBox(alignment: Alignment.center, child: repaintBoundary),
configuration: ViewConfiguration(
size: imageSize,
devicePixelRatio: 1.0,
),
);
final PipelineOwner pipelineOwner = PipelineOwner();
final BuildOwner buildOwner = BuildOwner(focusManager: FocusManager());
pipelineOwner.rootNode = renderView;
renderView.prepareInitialFrame();
final RenderObjectToWidgetElement<RenderBox> rootElement = RenderObjectToWidgetAdapter<RenderBox>(
container: repaintBoundary,
child: widget,
).attachToRenderTree(buildOwner);
buildOwner.buildScope(rootElement);
if (wait != null) {
await Future.delayed(wait);
}
buildOwner.buildScope(rootElement);
buildOwner.finalizeTree();
pipelineOwner.flushLayout();
pipelineOwner.flushCompositingBits();
pipelineOwner.flushPaint();
final ui.Image image = await repaintBoundary.toImage(pixelRatio: 1.0);
final ByteData byteData = (await image.toByteData(format: ui.ImageByteFormat.png))!;
return byteData.buffer.asUint8List();
}
