# MarkKeypoints

VTKExamples/Cxx/Images/MarkKeypoints

### Description

Thanks to Dean Inglis.

### Code

MarkKeypoints.cxx

    #include <vtkAbstractPicker.h>
    #include <vtkActor.h>
    #include <vtkActor2D.h>
    #include <vtkCoordinate.h>
    #include <vtkFollower.h>
    #include <vtkImageMapper3D.h>
    #include <vtkImageActor.h>
    #include <vtkImageCanvasSource2D.h>
    #include <vtkCoordinate.h>
    #include <vtkTransform.h>
    #include <vtkTransformPolyDataFilter.h>
    #include <vtkPolyDataMapper2D.h>

    //#include <vtkInteractorStyleTrackballCamera.h>
    #include <vtkInteractorStyleImage.h>
    #include <vtkObjectFactory.h>
    #include <vtkPolyData.h>
    #include <vtkPolyDataMapper.h>
    #include <vtkProperty.h>
    #include <vtkProperty2D.h>
    #include <vtkRenderWindow.h>
    #include <vtkRenderer.h>
    #include <vtkRendererCollection.h>
    #include <vtkRenderWindowInteractor.h>
    #include <vtkSphereSource.h>
    #include <vtkSmartPointer.h>
    #include <vtkVectorText.h>
    #include <vtkMath.h>
    #include <sstream>

    class MyStyle : public vtkInteractorStyleImage
    {
      public:
        static MyStyle* New();
        vtkTypeMacro(MyStyle, vtkInteractorStyleImage);

        std::vector<vtkActor2D*> Numbers;

        void OnLeftButtonDown()
        {

          //std::cout << "Picking pixel: " << this->Interactor->GetEventPosition()[0] << " " << this->Interactor->GetEventPosition()[1] << std::endl;
          this->Interactor->GetPicker()->Pick(this->Interactor->GetEventPosition()[0],
                  this->Interactor->GetEventPosition()[1],
                  0,  // always zero.
                  //this->Interactor->GetRenderWindow()->GetRenderers()->GetFirstRenderer());
                  this->CurrentRenderer );
          double picked[3];
          this->Interactor->GetPicker()->GetPickPosition(picked);
          //std::cout << "Picked point with coordinate: " << picked[0] << " " << picked[1] << " " << picked[2] << std::endl;

          this->AddNumber(picked);

          // Forward events
          vtkInteractorStyleImage::OnLeftButtonDown();

          //this->Interactor->GetRenderWindow()->Render();
          this->Interactor->Render();
        }

        void AddNumber(double p[3])
        {
          std::cout << "Adding marker at " << p[0] << " " << p[1] ;//<< std::endl;

          // normally, with an image you would do
          // double* s = image->GetSpacing();
          // double* o = image->GetOrigin();
          // p[0] = static_cast<int>( (p[0] - o[0]) / s[0] + 0.5 );
          p[0] = static_cast<int>( p[0] + 0.5 );
          p[1] = static_cast<int>( p[1] + 0.5 );

          std::cout << " -> " << p[0] << " " << p[1] << std::endl;

          // Convert the current number to a string
          std::stringstream ss;
          ss << Numbers.size();

          // Create an actor for the text
          vtkSmartPointer<vtkVectorText> textSource = vtkSmartPointer<vtkVectorText>::New();
          textSource->SetText( ss.str().c_str() );

          //get the bounds of the text
          textSource->Update();
          double* bounds = textSource->GetOutput()->GetBounds();
          //transform the polydata to be centered over the pick position
          double center[3] = {0.5*(bounds[1]+bounds[0]), 0.5*(bounds[3]+bounds[2]), 0.0 };

          vtkSmartPointer<vtkTransform> trans = vtkSmartPointer<vtkTransform>::New();
          trans->Translate( -center[0], -center[1], 0 );
          trans->Translate( p[0], p[1], 0 );

          vtkSmartPointer<vtkTransformPolyDataFilter> tpd = vtkSmartPointer<vtkTransformPolyDataFilter>::New();
          tpd->SetTransform( trans );
          tpd->SetInputConnection(  textSource->GetOutputPort() );

          // Create a mapper
          vtkSmartPointer<vtkPolyDataMapper2D> mapper = vtkSmartPointer<vtkPolyDataMapper2D>::New();
          vtkSmartPointer<vtkCoordinate> coordinate = vtkSmartPointer<vtkCoordinate>::New();
          coordinate->SetCoordinateSystemToWorld();
          mapper->SetTransformCoordinate( coordinate );
          mapper->SetInputConnection( tpd->GetOutputPort() );

          vtkSmartPointer<vtkActor2D> actor = vtkSmartPointer<vtkActor2D>::New();
          actor->SetMapper( mapper );
          actor->GetProperty()->SetColor( 1, 1, 0 ); // yellow

          this->CurrentRenderer->AddViewProp( actor );

          this->Numbers.push_back(actor);
        }

    };

    vtkStandardNewMacro(MyStyle);

    int main (int, char *[])
    {
      // Create a blank, black image
      vtkSmartPointer<vtkImageCanvasSource2D> drawing = vtkSmartPointer<vtkImageCanvasSource2D>::New();
      drawing->SetScalarTypeToUnsignedChar();
      drawing->SetNumberOfScalarComponents(3);
      drawing->SetExtent(0, 20, 0, 50, 0, 0);
      drawing->FillBox(0,20,0,50);

      // Draw a red circle of radius 5 centered at (9,10)
      drawing->SetDrawColor(255, 0, 0, 0);
      drawing->DrawCircle(9, 10, 5);
      drawing->Update();

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

      vtkSmartPointer<vtkRenderer> renderer = vtkSmartPointer<vtkRenderer>::New();
      vtkSmartPointer<vtkRenderWindow> renderWindow = vtkSmartPointer<vtkRenderWindow>::New();
      renderWindow->AddRenderer(renderer);

      vtkSmartPointer<vtkRenderWindowInteractor> renderWindowInteractor =
        vtkSmartPointer<vtkRenderWindowInteractor>::New();
      renderWindowInteractor->SetRenderWindow(renderWindow);

      renderer->AddActor(actor);
      renderer->SetBackground(1,1,1); // Background color white

      renderer->GradientBackgroundOn();
      renderer->SetBackground2(0,0,1); // Background 2 color blue

      renderWindow->Render();

      vtkSmartPointer<MyStyle> style = vtkSmartPointer<MyStyle>::New();

      renderWindowInteractor->SetInteractorStyle( style );
      style->SetDefaultRenderer( renderer );
      style->SetCurrentRenderer( renderer );
      renderWindowInteractor->Start();

      return EXIT_SUCCESS;
    }

### CMakeLists.txt

    cmake_minimum_required(VERSION 2.8)

    PROJECT(MarkKeypoints)

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

    add_executable(MarkKeypoints MACOSX_BUNDLE MarkKeypoints.cxx)

    target_link_libraries(MarkKeypoints ${VTK_LIBRARIES})

### Download and Build MarkKeypoints

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

    cd MarkKeypoints/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:

    ./MarkKeypoints

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.