ScalarBarWidget

#include <vtkActor.h>
#include <vtkCamera.h>
#include <vtkDataSetMapper.h>
#include <vtkLookupTable.h>
#include <vtkNamedColors.h>
#include <vtkNew.h>
#include <vtkRenderWindow.h>
#include <vtkRenderWindowInteractor.h>
#include <vtkRenderer.h>
#include <vtkScalarBarActor.h>
#include <vtkScalarBarWidget.h>
#include <vtkUnstructuredGrid.h>
#include <vtkUnstructuredGridReader.h>

#include <iostream>
#include <string>

int main(int argc, char* argv[])
{
  vtkNew<vtkNamedColors> colors;

  // Parse command line arguments.
  if (argc != 2)
  {
    std::cerr << "Usage: " << argv[0] << " Filename(.vtk) e.g.uGridEx.vtk"
              << std::endl;
    return EXIT_FAILURE;
  }

  // Create a custom lut. The lut is used for both the mapper and the
  // scalarBar.
  vtkNew<vtkLookupTable> lut;
  lut->Build();

  // Read the source file.
  vtkNew<vtkUnstructuredGridReader> reader;
  reader->SetFileName(argv[1]);
  reader->Update(); // Needed because of GetScalarRange.
  auto output = reader->GetOutput();
  auto scalarRange = output->GetScalarRange();

  vtkNew<vtkDataSetMapper> mapper;
  mapper->SetInputData(output);
  mapper->SetScalarRange(scalarRange);
  mapper->SetLookupTable(lut);

  vtkNew<vtkActor> actor;
  actor->SetMapper(mapper);

  vtkNew<vtkRenderer> renderer;
  renderer->AddActor(actor);
  renderer->SetBackground(colors->GetColor3d("MidnightBlue").GetData());

  vtkNew<vtkRenderWindow> renderWindow;
  renderWindow->AddRenderer(renderer);
  renderWindow->SetSize(300, 300);
  renderWindow->SetWindowName("ScalarBarWidget");

  vtkNew<vtkRenderWindowInteractor> interactor;
  interactor->SetRenderWindow(renderWindow);

  // Create the scalarBar.
  vtkNew<vtkScalarBarActor> scalarBar;
  scalarBar->SetOrientationToHorizontal();
  scalarBar->SetLookupTable(lut);

  // Create the scalarBarWidget.
  vtkNew<vtkScalarBarWidget> scalarBarWidget;
  scalarBarWidget->SetInteractor(interactor);
  scalarBarWidget->SetScalarBarActor(scalarBar);
  scalarBarWidget->On();

  interactor->Initialize();
  renderWindow->Render();
  renderer->GetActiveCamera()->SetPosition(-6.4, 10.3, 1.4);
  renderer->GetActiveCamera()->SetFocalPoint(1.0, 0.5, 3.0);
  renderer->GetActiveCamera()->SetViewUp(0.6, 0.4, -0.7);
  renderWindow->Render();
  interactor->Start();

  return EXIT_SUCCESS;
}

cmake_minimum_required(VERSION 3.12 FATAL_ERROR)

project(ScalarBarWidget)

find_package(VTK COMPONENTS 
)

if (NOT VTK_FOUND)
  message(FATAL_ERROR "ScalarBarWidget: Unable to find the VTK build folder.")
endif()

# Prevent a "command line is too long" failure in Windows.
set(CMAKE_NINJA_FORCE_RESPONSE_FILE "ON" CACHE BOOL "Force Ninja to use response files.")
add_executable(ScalarBarWidget MACOSX_BUNDLE ScalarBarWidget.cxx )
  target_link_libraries(ScalarBarWidget PRIVATE ${VTK_LIBRARIES}
)
# vtk_module_autoinit is needed
vtk_module_autoinit(
  TARGETS ScalarBarWidget
  MODULES ${VTK_LIBRARIES}
)

cd ScalarBarWidget/build

cmake ..

cmake -DVTK_DIR:PATH=/home/me/vtk_build ..

make

./ScalarBarWidget