# ImageNonMaximumSuppression

VTKExamples/Cxx/Images/ImageNonMaximumSuppression

### Code

ImageNonMaximumSuppression.cxx

    #include <vtkSmartPointer.h>
    #include <vtkInteractorStyleImage.h>
    #include <vtkImageActor.h>
    #include <vtkImageMapper3D.h>
    #include <vtkImageSinusoidSource.h>
    #include <vtkRenderWindow.h>
    #include <vtkRenderWindowInteractor.h>
    #include <vtkRenderer.h>
    #include <vtkImageGradient.h>
    #include <vtkImageGradientMagnitude.h>
    #include <vtkImageNonMaximumSuppression.h>
    #include <vtkImageCast.h>

    int main(int, char*[])
    {
      vtkSmartPointer<vtkImageSinusoidSource> source =
        vtkSmartPointer<vtkImageSinusoidSource>::New();
      source->Update();

      vtkSmartPointer<vtkImageCast> sourceCastFilter =
        vtkSmartPointer<vtkImageCast>::New();
      sourceCastFilter->SetOutputScalarTypeToUnsignedChar();
      sourceCastFilter->SetInputConnection(source->GetOutputPort());
      sourceCastFilter->Update();

      vtkSmartPointer<vtkImageGradient> gradientFilter =
        vtkSmartPointer<vtkImageGradient>::New();
      gradientFilter->SetInputConnection(source->GetOutputPort());

      vtkSmartPointer<vtkImageGradientMagnitude> gradientMagnitudeFilter =
        vtkSmartPointer<vtkImageGradientMagnitude>::New();
      gradientMagnitudeFilter->SetInputConnection(source->GetOutputPort());

      vtkSmartPointer<vtkImageCast> gradientMagnitudeCastFilter =
        vtkSmartPointer<vtkImageCast>::New();
      gradientMagnitudeCastFilter->SetOutputScalarTypeToUnsignedChar();
      gradientMagnitudeCastFilter->SetInputConnection(gradientMagnitudeFilter->GetOutputPort());
      gradientMagnitudeCastFilter->Update();

      vtkSmartPointer<vtkImageNonMaximumSuppression> suppressionFilter =
        vtkSmartPointer<vtkImageNonMaximumSuppression>::New();
      suppressionFilter->SetInputConnection(
        0, gradientMagnitudeFilter->GetOutputPort());
      suppressionFilter->SetInputConnection(
        1, gradientFilter->GetOutputPort());
      suppressionFilter->SetDimensionality(2);
      suppressionFilter->Update();

      vtkSmartPointer<vtkImageCast> suppressionCastFilter =
        vtkSmartPointer<vtkImageCast>::New();
      suppressionCastFilter->SetOutputScalarTypeToUnsignedChar();
      suppressionCastFilter->SetInputConnection(suppressionFilter->GetOutputPort());
      suppressionCastFilter->Update();

      // Create actors
      vtkSmartPointer<vtkImageActor> originalActor =
        vtkSmartPointer<vtkImageActor>::New();
      originalActor->GetMapper()->SetInputConnection(
        sourceCastFilter->GetOutputPort());

      vtkSmartPointer<vtkImageActor> gradientMagnitudeActor =
        vtkSmartPointer<vtkImageActor>::New();
      gradientMagnitudeActor->GetMapper()->SetInputConnection(
        gradientMagnitudeCastFilter->GetOutputPort());

      vtkSmartPointer<vtkImageActor> suppressionActor =
        vtkSmartPointer<vtkImageActor>::New();
      suppressionActor->GetMapper()->SetInputConnection(
        suppressionCastFilter->GetOutputPort());

      // Define viewport ranges
      // (xmin, ymin, xmax, ymax)
      double originalViewport[4] = {0.0, 0.0, 0.33, 1.0};
      double gradientMagnitudeViewport[4] = {0.33, 0.0, 0.66, 1.0};
      double suppressionViewport[4] = {0.66, 0.0, 1.0, 1.0};

      // Setup renderers
      vtkSmartPointer<vtkRenderer> originalRenderer =
        vtkSmartPointer<vtkRenderer>::New();
      originalRenderer->SetViewport(originalViewport);
      originalRenderer->AddActor(originalActor);
      originalRenderer->ResetCamera();
      originalRenderer->SetBackground(.4, .5, .6);

      vtkSmartPointer<vtkRenderer> gradientMagnitudeRenderer =
        vtkSmartPointer<vtkRenderer>::New();
      gradientMagnitudeRenderer->SetViewport(gradientMagnitudeViewport);
      gradientMagnitudeRenderer->AddActor(gradientMagnitudeActor);
      gradientMagnitudeRenderer->ResetCamera();
      gradientMagnitudeRenderer->SetBackground(.4, .5, .7);

      vtkSmartPointer<vtkRenderer> suppressionRenderer =
        vtkSmartPointer<vtkRenderer>::New();
      suppressionRenderer->SetViewport(suppressionViewport);
      suppressionRenderer->AddActor(suppressionActor);
      suppressionRenderer->ResetCamera();
      suppressionRenderer->SetBackground(.3, .5, .8);

      vtkSmartPointer<vtkRenderWindow> renderWindow =
        vtkSmartPointer<vtkRenderWindow>::New();
      renderWindow->SetSize(900, 300);
      renderWindow->AddRenderer(originalRenderer);
      renderWindow->AddRenderer(gradientMagnitudeRenderer);
      renderWindow->AddRenderer(suppressionRenderer);

      vtkSmartPointer<vtkRenderWindowInteractor> renderWindowInteractor =
        vtkSmartPointer<vtkRenderWindowInteractor>::New();
      vtkSmartPointer<vtkInteractorStyleImage> style =
        vtkSmartPointer<vtkInteractorStyleImage>::New();

      renderWindowInteractor->SetInteractorStyle(style);

      renderWindowInteractor->SetRenderWindow(renderWindow);
      renderWindow->Render();
      renderWindowInteractor->Initialize();

      renderWindowInteractor->Start();

      return EXIT_SUCCESS;
    }

### CMakeLists.txt

    cmake_minimum_required(VERSION 3.3 FATAL_ERROR)

    project(ImageNonMaximumSuppression)

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

### Download and Build ImageNonMaximumSuppression

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

    cd ImageNonMaximumSuppression/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:

    ./ImageNonMaximumSuppression

WINDOWS USERS

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