获取render以及actor

渲染串口可以添加多个render

  vtkScalarBarActor* scalarBar = nullptr;
  vtkRendererCollection* renderers = ui->widget_color->GetRenderWindow()->GetRenderers();
  renderers->InitTraversal();
  while (vtkRenderer* renderer = renderers->GetNextItem()) {
      vtkActorCollection* actors = renderer->GetActors();
      actors->InitTraversal();
      while (vtkActor* actor = actors->GetNextItem()) {
          scalarBar = vtkScalarBarActor::SafeDownCast(actor);
          if (scalarBar) {
              break;
          }
      }
  }