# HybridMedianComparison

VTKExamples/Cxx/ImageProcessing/HybridMedianComparison

### Description

Comparison of median and hybrid-median filters. The hybrid filter preserves corners and thin lines, better than the median filter. The lower patterns represent the three neighborhoods used to compute the hybrid median.

Info

See this figure in Chapter 10 the VTK Textbook.

Other Languages

See (Python)

### Code

HybridMedianComparison.cxx

    #include <vtkCamera.h>
    #include <vtkDataArray.h>
    #include <vtkImageActor.h>
    #include <vtkImageCast.h>
    #include <vtkImageData.h>
    #include <vtkImageHybridMedian2D.h>
    #include <vtkImageMapper3D.h>
    #include <vtkImageMathematics.h>
    #include <vtkImageMedian3D.h>
    #include <vtkImageNoiseSource.h>
    #include <vtkImageProperty.h>
    #include <vtkImageReader2.h>
    #include <vtkImageReader2Factory.h>
    #include <vtkImageReader2Factory.h>
    #include <vtkImageThreshold.h>
    #include <vtkInteractorStyleImage.h>
    #include <vtkPointData.h>
    #include <vtkRenderer.h>
    #include <vtkRenderWindow.h>
    #include <vtkRenderWindowInteractor.h>
    #include <vtkSmartPointer.h>

    #include <vector>

    namespace
    {
    void AddShotNoise(vtkSmartPointer<vtkImageData> &inputImage,
                      vtkSmartPointer<vtkImageData> &outputImage,
                      double amplitude,
                      double noiseFraction,
                      int extent[6]);
    }
    int main (int argc, char *argv[])
    {
      // Verify input arguments
      if ( argc != 2 )
      {
        std::cout << "Usage: " << argv[0]
                  << " Filename" << std::endl;
        return EXIT_FAILURE;
      }

      // Read the image
      vtkSmartPointer<vtkImageReader2Factory> readerFactory =
        vtkSmartPointer<vtkImageReader2Factory>::New();
      vtkSmartPointer<vtkImageReader2> reader =
        readerFactory->CreateImageReader2(argv[1]);
      reader->SetFileName(argv[1]);
      reader->Update();

      int scalarRange[2];
      scalarRange[0] =
        reader->GetOutput()->GetPointData()->GetScalars()->GetRange()[0];
      scalarRange[1] =
        reader->GetOutput()->GetPointData()->GetScalars()->GetRange()[1];
      std::cout << "Range: "
                << scalarRange[0] << ", " << scalarRange[1]
                << std::endl;
      int middleSlice = (reader->GetOutput()->GetExtent()[5] -
                         reader->GetOutput()->GetExtent()[4]) / 2;

      // Work with double images
      vtkSmartPointer<vtkImageCast> cast =
        vtkSmartPointer<vtkImageCast>::New();
      cast->SetInputConnection(reader->GetOutputPort());
      cast->SetOutputScalarTypeToDouble();
      cast->Update();

      vtkSmartPointer<vtkImageData> originalData =
        vtkSmartPointer<vtkImageData>::New();
      originalData->DeepCopy(cast->GetOutput());

      vtkSmartPointer<vtkImageData> noisyData =
        vtkSmartPointer<vtkImageData>::New();

      AddShotNoise(originalData, noisyData,
                   2000.0, .1, reader->GetOutput()->GetExtent());
      vtkSmartPointer<vtkImageMedian3D> median =
        vtkSmartPointer<vtkImageMedian3D>::New();
      median->SetInputData(noisyData);
      median->SetKernelSize(5, 5, 1);

      vtkSmartPointer<vtkImageHybridMedian2D> hybridMedian1 =
        vtkSmartPointer<vtkImageHybridMedian2D>::New();
      hybridMedian1->SetInputData(noisyData);
      vtkSmartPointer<vtkImageHybridMedian2D> hybridMedian =
        vtkSmartPointer<vtkImageHybridMedian2D>::New();
      hybridMedian->SetInputConnection(hybridMedian1->GetOutputPort());

      int colorWindow = (scalarRange[1] - scalarRange[0]);
      int colorLevel = colorWindow / 2;
      vtkSmartPointer<vtkImageActor> originalActor =
        vtkSmartPointer<vtkImageActor>::New();
      originalActor->GetMapper()->SetInputData(originalData);
      originalActor->GetProperty()->SetColorWindow(colorWindow);
      originalActor->GetProperty()->SetColorLevel(colorLevel);
      originalActor->GetProperty()->SetInterpolationTypeToNearest();
      originalActor->SetDisplayExtent(
        reader->GetDataExtent()[0], reader->GetDataExtent()[1],
        reader->GetDataExtent()[2], reader->GetDataExtent()[3],
        middleSlice, middleSlice);

      vtkSmartPointer<vtkImageActor> noisyActor =
        vtkSmartPointer<vtkImageActor>::New();
      noisyActor->GetMapper()->SetInputData(noisyData);
      noisyActor->GetProperty()->SetColorWindow(colorWindow);
      noisyActor->GetProperty()->SetColorLevel(colorLevel);
      noisyActor->GetProperty()->SetInterpolationTypeToNearest();
      noisyActor->SetDisplayExtent(originalActor->GetDisplayExtent());

      vtkSmartPointer<vtkImageActor> hybridMedianActor =
        vtkSmartPointer<vtkImageActor>::New();
      hybridMedianActor->GetMapper()->SetInputConnection(hybridMedian->GetOutputPort());
      hybridMedianActor->GetProperty()->SetColorWindow(colorWindow);
      hybridMedianActor->GetProperty()->SetColorLevel(colorLevel);
      hybridMedianActor->GetProperty()->SetInterpolationTypeToNearest();
      hybridMedianActor->SetDisplayExtent(originalActor->GetDisplayExtent());

      vtkSmartPointer<vtkImageActor> medianActor =
        vtkSmartPointer<vtkImageActor>::New();
      medianActor->GetMapper()->SetInputConnection(median->GetOutputPort());
      medianActor->GetProperty()->SetColorWindow(colorWindow);
      medianActor->GetProperty()->SetColorLevel(colorLevel);
      medianActor->GetProperty()->SetInterpolationTypeToNearest();
      medianActor->SetDisplayExtent(originalActor->GetDisplayExtent());

      // Setup renderers
      vtkSmartPointer<vtkRenderer> originalRenderer =
        vtkSmartPointer<vtkRenderer>::New();
      originalRenderer->AddActor(originalActor);
      vtkSmartPointer<vtkRenderer> noisyRenderer =
        vtkSmartPointer<vtkRenderer>::New();
      noisyRenderer->AddActor(noisyActor);
      vtkSmartPointer<vtkRenderer> hybridRenderer =
        vtkSmartPointer<vtkRenderer>::New();
      hybridRenderer->AddActor(hybridMedianActor);
      vtkSmartPointer<vtkRenderer> medianRenderer =
        vtkSmartPointer<vtkRenderer>::New();
      medianRenderer->AddActor(medianActor);

      std::vector<vtkSmartPointer<vtkRenderer> > renderers;
      renderers.push_back(originalRenderer);
      renderers.push_back(noisyRenderer);
      renderers.push_back(hybridRenderer);
      renderers.push_back(medianRenderer);

      // Setup viewports for the renderers
      int rendererSize = 400;
      unsigned int xGridDimensions = 2;
      unsigned int yGridDimensions = 2;

      vtkSmartPointer<vtkRenderWindow> renderWindow =
        vtkSmartPointer<vtkRenderWindow>::New();
      renderWindow->SetSize(
        rendererSize * xGridDimensions, rendererSize * yGridDimensions);
      for (int row = 0; row < static_cast<int>(yGridDimensions); row++)
      {
        for (int col = 0; col < static_cast<int>(xGridDimensions); col++)
        {
          int index = row * xGridDimensions + col;
          // (xmin, ymin, xmax, ymax)
           double viewport[4] = {
             static_cast<double>(col) / xGridDimensions,
             static_cast<double>(yGridDimensions - (row + 1)) / yGridDimensions,
             static_cast<double>(col + 1) / xGridDimensions,
             static_cast<double>(yGridDimensions - row) / yGridDimensions};
          renderers[index]->SetViewport(viewport);
          renderWindow->AddRenderer(renderers[index]);
        }
      }

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

      renderWindowInteractor->SetInteractorStyle(style);
      renderWindowInteractor->SetRenderWindow(renderWindow);

      // Renderers share one camera
      renderWindow->Render();
      renderers[0]->GetActiveCamera()->Dolly(1.5);
      renderers[0]->ResetCameraClippingRange();

      for (size_t r = 1; r < renderers.size(); ++r)
      {
        renderers[r]->SetActiveCamera(renderers[0]->GetActiveCamera());
      }
      renderWindowInteractor->Initialize();
      renderWindowInteractor->Start();

      return EXIT_SUCCESS;
    }
    namespace
    {
    void AddShotNoise(vtkSmartPointer<vtkImageData> &inputImage,
                      vtkSmartPointer<vtkImageData> &outputImage,
                      double noiseAmplitude,
                      double noiseFraction,
                      int extent[6])
    {
      vtkSmartPointer<vtkImageNoiseSource> shotNoiseSource =
        vtkSmartPointer<vtkImageNoiseSource>::New();
      shotNoiseSource->SetWholeExtent(extent);
      shotNoiseSource->SetMinimum(0.0);
      shotNoiseSource->SetMaximum(1.0);

      vtkSmartPointer<vtkImageThreshold> shotNoiseThresh1 =
        vtkSmartPointer<vtkImageThreshold>::New();
      shotNoiseThresh1->SetInputConnection(shotNoiseSource->GetOutputPort());
      shotNoiseThresh1->ThresholdByLower(1.0 - noiseFraction);
      shotNoiseThresh1->SetInValue(0);
      shotNoiseThresh1->SetOutValue(noiseAmplitude);

      vtkSmartPointer<vtkImageThreshold> shotNoiseThresh2 =
        vtkSmartPointer<vtkImageThreshold>::New();
      shotNoiseThresh2->SetInputConnection(shotNoiseSource->GetOutputPort());
      shotNoiseThresh2->ThresholdByLower(noiseFraction);
      shotNoiseThresh2->SetInValue(1.0 - noiseAmplitude);
      shotNoiseThresh2->SetOutValue(0.0);

      vtkSmartPointer<vtkImageMathematics> shotNoise =
        vtkSmartPointer<vtkImageMathematics>::New();
      shotNoise->SetInputConnection(0, shotNoiseThresh1->GetOutputPort());
      shotNoise->SetInputConnection(1, shotNoiseThresh2->GetOutputPort());
      shotNoise->SetOperationToAdd();

      vtkSmartPointer<vtkImageMathematics> add =
        vtkSmartPointer<vtkImageMathematics>::New();
      add->SetInputData(0, inputImage);
      add->SetInputConnection(1, shotNoise->GetOutputPort());
      add->SetOperationToAdd();
      add->Update();
      outputImage->DeepCopy(add->GetOutput());
    }
    }

### CMakeLists.txt

    cmake_minimum_required(VERSION 3.3 FATAL_ERROR)

    project(HybridMedianComparison)

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

### Download and Build HybridMedianComparison

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

    cd HybridMedianComparison/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:

    ./HybridMedianComparison

WINDOWS USERS

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