# ImageTracerWidget

VTKExamples/Cxx/Widgets/ImageTracerWidget

### Code

ImageTracerWidget.cxx

    #include <vtkSmartPointer.h>
    #include <vtkCallbackCommand.h>
    #include <vtkImageActor.h>
    #include <vtkPolyDataMapper.h>
    #include <vtkActor.h>
    #include <vtkRenderWindow.h>
    #include <vtkRenderer.h>
    #include <vtkRenderWindowInteractor.h>
    #include <vtkPolyData.h>
    #include <vtkSphereSource.h>
    #include <vtkImageTracerWidget.h>
    #include <vtkImageMapper3D.h>
    #include <vtkImageCanvasSource2D.h>
    #include <vtkInteractorStyleImage.h>
    #include <vtkProperty.h>

    namespace
    {
    void CallbackFunction (vtkObject* caller, long unsigned int eventId,
                            void* clientData, void* callData );
    }

    int main(int, char *[])
    {
      vtkSmartPointer<vtkImageCanvasSource2D> imageSource =
        vtkSmartPointer<vtkImageCanvasSource2D>::New();
      imageSource->SetScalarTypeToUnsignedChar();
      imageSource->SetNumberOfScalarComponents(3);
      imageSource->SetExtent(0, 20, 0, 50, 0, 0);
      imageSource->SetDrawColor(0,0,0);
      imageSource->FillBox(0,20,0,50);
      imageSource->SetDrawColor(255,0,0);
      imageSource->FillBox(0,10,0,30);
      imageSource->Update();

      vtkSmartPointer<vtkImageActor> actor =
        vtkSmartPointer<vtkImageActor>::New();
      actor->GetMapper()->SetInputConnection(imageSource->GetOutputPort());

      vtkSmartPointer<vtkRenderer> renderer =
        vtkSmartPointer<vtkRenderer>::New();
      renderer->AddActor(actor);
      renderer->ResetCamera();
      vtkSmartPointer<vtkRenderWindow> renderWindow =
        vtkSmartPointer<vtkRenderWindow>::New();
      renderWindow->AddRenderer(renderer);
      vtkSmartPointer<vtkRenderWindowInteractor> interactor =
        vtkSmartPointer<vtkRenderWindowInteractor>::New();
      interactor->SetRenderWindow(renderWindow);

      vtkSmartPointer<vtkInteractorStyleImage> style =
        vtkSmartPointer<vtkInteractorStyleImage>::New();
      interactor->SetInteractorStyle(style);

      vtkSmartPointer<vtkImageTracerWidget> tracer =
        vtkSmartPointer<vtkImageTracerWidget>::New();
      tracer->GetLineProperty()->SetLineWidth(5);
      tracer->SetInteractor(interactor);
      tracer->SetViewProp(actor);
      renderWindow->Render();

      // The observer must be added BEFORE the On() call.
      vtkSmartPointer<vtkCallbackCommand> callback =
        vtkSmartPointer<vtkCallbackCommand>::New();
      callback->SetCallback(CallbackFunction);
      tracer->AddObserver(vtkCommand::EndInteractionEvent, callback);

      tracer->On();
      interactor->Start();

      return EXIT_SUCCESS;
    }

    namespace
    {
    void CallbackFunction (vtkObject* caller,
                           long unsigned int vtkNotUsed(eventId),
                           void* vtkNotUsed(clientData),
                           void* vtkNotUsed(callData) )
    {
      vtkImageTracerWidget* tracerWidget =
        static_cast<vtkImageTracerWidget*>(caller);

      vtkSmartPointer<vtkPolyData> path =
        vtkSmartPointer<vtkPolyData>::New();

      tracerWidget->GetPath(path);
      std::cout << "There are " << path->GetNumberOfPoints() << " points in the path." << std::endl;
    }
    } // end anonymous namespace

### CMakeLists.txt

    cmake_minimum_required(VERSION 2.8)

    PROJECT(ImageTracerWidget)

    find_package(VTK REQUIRED)
    include(${VTK_USE_FILE})

    add_executable(ImageTracerWidget MACOSX_BUNDLE ImageTracerWidget.cxx )

    target_link_libraries(ImageTracerWidget ${VTK_LIBRARIES})

### Download and Build ImageTracerWidget

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

    cd ImageTracerWidget/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:

    ./ImageTracerWidget

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