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# SelectWindowRegion

VTKEx/Cxx/Visualization/SelectWindowRegion

Question

If you have a simple question about this example contact us at VTKExProject If your question is more complex and may require extended discussion, please use the VTK Discourse Forum

### Code

SelectWindowRegion.cxx

    #include <vtkSmartPointer.h>

    #include <vtkCallbackCommand.h>
    #include <vtkCommand.h>
    #include <vtkImageActor.h>
    #include <vtkImageMapper3D.h>
    #include <vtkInteractorStyleRubberBand2D.h>
    #include <vtkJPEGReader.h>
    #include <vtkRenderWindow.h>
    #include <vtkRenderWindowInteractor.h>
    #include <vtkRenderer.h>

    static void SelectionChangedCallbackFunction (
      vtkObject* caller,
      long unsigned int eventId,
      void* clientData,
      void* callData );

    int main(int argc, char* argv[])
    {
      // Parse input arguments
      if ( argc != 2 )
      {
        std::cout << "Required parameters: Filename" << std::endl;
        return EXIT_FAILURE;
      }

      std::string inputFilename = argv[1];

      // Read the image
      vtkSmartPointer<vtkJPEGReader> jPEGReader =
        vtkSmartPointer<vtkJPEGReader>::New();
      jPEGReader->SetFileName ( inputFilename.c_str() );
      jPEGReader->Update();

      // Create an actor
      vtkSmartPointer<vtkImageActor> actor =
        vtkSmartPointer<vtkImageActor>::New();
      actor->GetMapper()->SetInputConnection ( jPEGReader->GetOutputPort() );

      // Setup the SelectionChangedEvent callback
      vtkSmartPointer<vtkCallbackCommand> selectionChangedCallback =
        vtkSmartPointer<vtkCallbackCommand>::New();
      selectionChangedCallback->SetCallback ( SelectionChangedCallbackFunction );

      // Setup renderer
      vtkSmartPointer<vtkRenderer> renderer =
        vtkSmartPointer<vtkRenderer>::New();
      renderer->AddActor ( actor );
      renderer->ResetCamera();

      // Setup render window
      vtkSmartPointer<vtkRenderWindow> renderWindow =
        vtkSmartPointer<vtkRenderWindow>::New();
      renderWindow->AddRenderer ( renderer );

      // Setup 2D interaction style
      vtkSmartPointer<vtkInteractorStyleRubberBand2D> style =
        vtkSmartPointer<vtkInteractorStyleRubberBand2D>::New();
      style->AddObserver ( vtkCommand::SelectionChangedEvent, selectionChangedCallback );

      // Setup render window interactor
      vtkSmartPointer<vtkRenderWindowInteractor> renderWindowInteractor =
        vtkSmartPointer<vtkRenderWindowInteractor>::New();
      renderWindowInteractor->SetInteractorStyle ( style );

      // Render and start interaction
      renderWindowInteractor->SetRenderWindow ( renderWindow );
      renderWindow->Render();
      renderWindowInteractor->Initialize();

      renderWindowInteractor->Start();

      return EXIT_SUCCESS;
    }

    void SelectionChangedCallbackFunction (
      vtkObject* vtkNotUsed(caller),
      long unsigned int vtkNotUsed(eventId),
      void* vtkNotUsed(clientData),
      void* callData )
    {
      std::cout << "Selection changed callback" << std::endl;

      unsigned int* rect = reinterpret_cast<unsigned int*> ( callData );
      unsigned int pos1X = rect[0];
      unsigned int pos1Y = rect[1];
      unsigned int pos2X = rect[2];
      unsigned int pos2Y = rect[3];

      std::cout << "Start x: " << pos1X
                << " Start y: " << pos1Y
                << " End x: " << pos2X
                << " End y: " << pos2Y << std::endl;
    }

    /*
    //You could override this, but then you have to reimplement the functionality.
    //Instead, you should use an observer

    void vtkInteractorStyleRubberBand2D::OnLeftButtonUp()
    {
      std::cout << "LeftButtonUp!" << std::endl;

      std::cout << "Start: " << this->StartPosition[0] << " " << this->StartPosition[1] << std::endl;
      std::cout << "End: " << this->EndPosition[0] << " " << this->EndPosition[1] << std::endl;

      //this->Superclass.OnLeftButtonUp(); //doesn't work

      InvokeEvent(vtkCommand::EndPickEvent);
      InvokeEvent(vtkCommand::SelectionChangedEvent);

    }
    */

### CMakeLists.txt

    cmake_minimum_required(VERSION 3.3 FATAL_ERROR)

    project(SelectWindowRegion)

    find_package(VTK COMPONENTS
      vtkCommonCore
      vtkIOImage
      vtkInteractionStyle
      vtkRenderingContextOpenGL2
      vtkRenderingCore
      vtkRenderingFreeType
      vtkRenderingGL2PSOpenGL2
      vtkRenderingOpenGL2 QUIET)
    if (NOT VTK_FOUND)
      message("Skipping SelectWindowRegion: ${VTK_NOT_FOUND_MESSAGE}")
      return ()
    endif()
    message (STATUS "VTK_VERSION: ${VTK_VERSION}")
    if (VTK_VERSION VERSION_LESS "8.90.0")
      # old system
      include(${VTK_USE_FILE})
      add_executable(SelectWindowRegion MACOSX_BUNDLE SelectWindowRegion.cxx )
      target_link_libraries(SelectWindowRegion PRIVATE ${VTK_LIBRARIES})
    else ()
      # include all components
      add_executable(SelectWindowRegion MACOSX_BUNDLE SelectWindowRegion.cxx )
      target_link_libraries(SelectWindowRegion PRIVATE ${VTK_LIBRARIES})
      # vtk_module_autoinit is needed
      vtk_module_autoinit(
        TARGETS SelectWindowRegion
        MODULES ${VTK_LIBRARIES}
        )
    endif ()

### Download and Build SelectWindowRegion

Click here to download SelectWindowRegion and its CMakeLists.txt file. Once the tarball SelectWindowRegion.tar has been downloaded and extracted,

    cd SelectWindowRegion/build

If VTK is installed:

    cmake ..

If VTK is not installed but compiled on your system, you will need to specify the path to your VTK build:

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

Build the project:

    make

and run it:

    ./SelectWindowRegion

WINDOWS USERS

Be sure to add the VTK bin directory to your path. This will resolve the VTK dll's at run time.