# ThinPlateSplineTransform

VTKExamples/Cxx/PolyData/ThinPlateSplineTransform

### Code

ThinPlateSplineTransform.cxx

    #include <vtkImageGridSource.h>
    #include <vtkLookupTable.h>
    #include <vtkImageMapToColors.h>
    #include <vtkBMPReader.h>
    #include <vtkImageBlend.h>
    #include <vtkPoints.h>
    #include <vtkThinPlateSplineTransform.h>
    #include <vtkImageReslice.h>
    #include <vtkSmartPointer.h>
    #include <vtkDataObject.h>
    #include <vtkRenderer.h>
    #include <vtkRenderWindow.h>
    #include <vtkRenderWindowInteractor.h>
    #include <vtkInteractorStyleTerrain.h>
    #include <vtkImageMapper.h>
    #include <vtkActor2D.h>

    // Warp an image with a thin plate spline

    int main(int argc, char *argv[])
    {
      if ( argc < 2 )
      {
        std::cerr << "Usage: " << argv[0] << " Filename.bmp" << std::endl;
        return EXIT_FAILURE;
      }

      // First, create an image to warp
      vtkSmartPointer<vtkImageGridSource> imageGrid =
        vtkSmartPointer<vtkImageGridSource >::New();
      imageGrid->SetGridSpacing( 16, 16, 0 );
      imageGrid->SetGridOrigin( 0, 0, 0 );
      imageGrid->SetDataExtent( 0, 255, 0, 255, 0, 0 );
      imageGrid->SetDataScalarTypeToUnsignedChar();

      vtkSmartPointer<vtkLookupTable> table =
        vtkSmartPointer<vtkLookupTable >::New();
      table->SetTableRange( 0, 1 );
      table->SetAlphaRange( 0.0, 1.0 );
      table->SetHueRange( 0.15, 0.15 );
      table->SetSaturationRange( 1, 1 );
      table->SetValueRange( 0, 1 );
      table->Build();

      vtkSmartPointer<vtkImageMapToColors> alpha =
        vtkSmartPointer<vtkImageMapToColors >::New();
      alpha->SetInputConnection( imageGrid->GetOutputPort() );
      alpha->SetLookupTable( table );

      vtkSmartPointer<vtkBMPReader> reader =
        vtkSmartPointer<vtkBMPReader>::New();
      reader->SetFileName(argv[1]);
      reader->Update();

      vtkSmartPointer<vtkImageBlend> blend =
        vtkSmartPointer<vtkImageBlend >::New();
      blend->AddInputConnection( 0, reader->GetOutputPort() );
      blend->AddInputConnection( 0, alpha->GetOutputPort() );

      // Next, create a ThinPlateSpline transform

      vtkSmartPointer< vtkPoints > p1 = vtkSmartPointer< vtkPoints >::New();
      p1->SetNumberOfPoints( 8 );
      p1->SetPoint( 0, 0, 0, 0 );
      p1->SetPoint( 1, 0, 255, 0);
      p1->SetPoint( 2, 255, 0, 0 );
      p1->SetPoint( 3, 255, 255, 0 );
      p1->SetPoint( 4, 96, 96, 0 );
      p1->SetPoint( 5, 96, 159, 0 );
      p1->SetPoint( 6, 159, 159, 0 );
      p1->SetPoint( 7, 159, 96, 0 );

      vtkSmartPointer< vtkPoints > p2 = vtkSmartPointer< vtkPoints >::New();
      p2->SetNumberOfPoints( 8 );
      p2->SetPoint( 0, 0, 0, 0 );
      p2->SetPoint( 1, 0, 255, 0 );
      p2->SetPoint( 2, 255, 0, 0 );
      p2->SetPoint( 3, 255, 255, 0);
      p2->SetPoint( 4, 96, 159, 0 );
      p2->SetPoint( 5, 159, 159, 0 );
      p2->SetPoint( 6, 159, 96, 0 );
      p2->SetPoint( 7, 96, 96, 0 );

      vtkSmartPointer<vtkThinPlateSplineTransform> transform =
        vtkSmartPointer< vtkThinPlateSplineTransform >::New();
      transform->SetSourceLandmarks( p2 );
      transform->SetTargetLandmarks( p1 );
      transform->SetBasisToR2LogR();
      // You must invert the transform before passing it to vtkImageReslice
      transform->Inverse();

      vtkSmartPointer< vtkImageReslice > reslice =
        vtkSmartPointer<vtkImageReslice >::New();
      reslice->SetInputConnection( blend->GetOutputPort() );
      reslice->SetResliceTransform( transform );
      reslice->SetInterpolationModeToLinear();
      vtkSmartPointer< vtkImageMapper > map =
        vtkSmartPointer<vtkImageMapper >::New();
      map->SetInputConnection( reslice->GetOutputPort() );
      map->SetColorWindow( 255.0);
      map->SetColorLevel( 127.5 );
      map->SetZSlice( 0 );
      vtkSmartPointer< vtkActor2D > act =
        vtkSmartPointer< vtkActor2D >::New();
      act->SetMapper( map );
      act->SetPosition( 0.0, 0.0 );

      vtkSmartPointer< vtkRenderer > renderer =
        vtkSmartPointer<vtkRenderer >::New();
      renderer->AddActor( act );
      vtkSmartPointer< vtkRenderWindow > window =
        vtkSmartPointer<vtkRenderWindow >::New();
      window->SetSize( 640, 480 );
      window->AddRenderer(renderer);
      vtkSmartPointer< vtkRenderWindowInteractor > interactor =
        vtkSmartPointer< vtkRenderWindowInteractor >::New();
      interactor->SetRenderWindow(window);
      vtkSmartPointer< vtkInteractorStyleTerrain > style =
        vtkSmartPointer< vtkInteractorStyleTerrain >::New();
      interactor->SetInteractorStyle( style );
      window->Render();
      interactor->Initialize();
      interactor->Start();

      return EXIT_SUCCESS;
    }

### CMakeLists.txt

    cmake_minimum_required(VERSION 3.3 FATAL_ERROR)

    project(ThinPlateSplineTransform)

    find_package(VTK COMPONENTS
      vtkCommonCore
      vtkCommonDataModel
      vtkCommonTransforms
      vtkIOImage
      vtkImagingCore
      vtkImagingSources
      vtkInteractionStyle
      vtkRenderingContextOpenGL2
      vtkRenderingCore
      vtkRenderingFreeType
      vtkRenderingGL2PSOpenGL2
      vtkRenderingOpenGL2 QUIET)
    if (NOT VTK_FOUND)
      message("Skipping ThinPlateSplineTransform: ${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(ThinPlateSplineTransform MACOSX_BUNDLE ThinPlateSplineTransform.cxx )
      target_link_libraries(ThinPlateSplineTransform PRIVATE ${VTK_LIBRARIES})
    else ()
      # include all components
      add_executable(ThinPlateSplineTransform MACOSX_BUNDLE ThinPlateSplineTransform.cxx )
      target_link_libraries(ThinPlateSplineTransform PRIVATE ${VTK_LIBRARIES})
      # vtk_module_autoinit is needed
      vtk_module_autoinit(
        TARGETS ThinPlateSplineTransform
        MODULES ${VTK_LIBRARIES}
        )
    endif ()

### Download and Build ThinPlateSplineTransform

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

    cd ThinPlateSplineTransform/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:

    ./ThinPlateSplineTransform

WINDOWS USERS

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