# ImageIdealHighPass

VTKExamples/Cxx/Images/ImageIdealHighPass

### Code

ImageIdealHighPass.cxx

    #include <vtkImageExtractComponents.h>
    #include <vtkImageData.h>
    #include <vtkImageFFT.h>
    #include <vtkImageMandelbrotSource.h>
    #include <vtkImageIdealHighPass.h>
    #include <vtkImageShiftScale.h>
    #include <vtkInteractorStyleImage.h>
    #include <vtkImageSlice.h>
    #include <vtkImageSliceMapper.h>
    #include <vtkImageEllipsoidSource.h>
    #include <vtkImageCast.h>
    #include <vtkImageRFFT.h>
    #include <vtkRenderer.h>
    #include <vtkRenderWindow.h>
    #include <vtkRenderWindowInteractor.h>
    #include <vtkSmartPointer.h>

    int main(int, char *[])
    {
      // Create an image
      vtkSmartPointer<vtkImageMandelbrotSource> mandelbrotSource =
              vtkSmartPointer<vtkImageMandelbrotSource>::New();
      mandelbrotSource->Update();

      // Display the original image
      vtkSmartPointer<vtkImageCast> originalCastFilter =
              vtkSmartPointer<vtkImageCast>::New();
      originalCastFilter->SetInputConnection(mandelbrotSource->GetOutputPort());
      originalCastFilter->SetOutputScalarTypeToUnsignedChar();
      originalCastFilter->Update();

      vtkSmartPointer<vtkImageSliceMapper> originalSliceMapper =
              vtkSmartPointer<vtkImageSliceMapper>::New();
      originalSliceMapper->SetInputConnection(originalCastFilter->GetOutputPort());

      vtkSmartPointer<vtkImageSlice> originalSlice =
              vtkSmartPointer<vtkImageSlice>::New();
      originalSlice->SetMapper(originalSliceMapper);

      // Compute the FFT of the image
      vtkSmartPointer<vtkImageFFT> fftFilter =
              vtkSmartPointer<vtkImageFFT>::New();
      fftFilter->SetInputConnection(originalCastFilter->GetOutputPort());
      fftFilter->Update();

      // High pass filter the FFT
      vtkSmartPointer<vtkImageIdealHighPass> highPassFilter =
              vtkSmartPointer<vtkImageIdealHighPass>::New();
      highPassFilter->SetInputConnection(fftFilter->GetOutputPort());
      highPassFilter->SetXCutOff(.1);
      highPassFilter->SetYCutOff(.1);
      highPassFilter->Update();

      // Compute the IFFT of the high pass filtered image
      vtkSmartPointer<vtkImageRFFT> rfftFilter =
              vtkSmartPointer<vtkImageRFFT>::New();
      rfftFilter->SetInputConnection(highPassFilter->GetOutputPort());
      rfftFilter->Update();

      vtkSmartPointer<vtkImageExtractComponents> extractRealFilter =
        vtkSmartPointer<vtkImageExtractComponents>::New();
      extractRealFilter->SetInputConnection(rfftFilter->GetOutputPort());
      extractRealFilter->SetComponents(0);
      extractRealFilter->Update();

      vtkSmartPointer<vtkImageShiftScale> shiftScaleFilter =
        vtkSmartPointer<vtkImageShiftScale>::New();
      shiftScaleFilter->SetOutputScalarTypeToUnsignedChar();
      shiftScaleFilter->SetInputConnection(extractRealFilter->GetOutputPort());
      shiftScaleFilter->SetShift(-1.0f * extractRealFilter->GetOutput()->GetScalarRange()[0]); // brings the lower bound to 0
      float oldRange = extractRealFilter->GetOutput()->GetScalarRange()[1] -
              extractRealFilter->GetOutput()->GetScalarRange()[0];
      float newRange = 100; // We want the output [0,100] (the same as the original image)
      shiftScaleFilter->SetScale(newRange/oldRange);
      shiftScaleFilter->Update();

      // Cast the output back to unsigned char
      vtkSmartPointer<vtkImageCast> outputCastFilter =
              vtkSmartPointer<vtkImageCast>::New();
      outputCastFilter->SetInputConnection(shiftScaleFilter->GetOutputPort());
      outputCastFilter->SetOutputScalarTypeToUnsignedChar();
      outputCastFilter->Update();

      // Display the high pass filtered image
      vtkSmartPointer<vtkImageSliceMapper> highPassSliceMapper =
              vtkSmartPointer<vtkImageSliceMapper>::New();
      highPassSliceMapper->SetInputConnection(outputCastFilter->GetOutputPort());

      vtkSmartPointer<vtkImageSlice> highPassSlice =
              vtkSmartPointer<vtkImageSlice>::New();
      highPassSlice->SetMapper(highPassSliceMapper);

      // Define viewport ranges
      // (xmin, ymin, xmax, ymax)
      double originalViewport[4] = {0.0, 0.0, 0.5, 1.0};
      double highPassViewport[4] = {0.5, 0.0, 1.0, 1.0};

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

      vtkSmartPointer<vtkRenderer> highPassRenderer =
        vtkSmartPointer<vtkRenderer>::New();
      highPassRenderer->SetViewport(highPassViewport);
      highPassRenderer->AddViewProp(highPassSlice);
      highPassRenderer->ResetCamera();
      highPassRenderer->SetBackground(.4, .5, .7);

      vtkSmartPointer<vtkRenderWindow> renderWindow =
        vtkSmartPointer<vtkRenderWindow>::New();
      renderWindow->SetSize(600, 300);
      renderWindow->AddRenderer(originalRenderer);
      renderWindow->AddRenderer(highPassRenderer);

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

      renderWindowInteractor->SetInteractorStyle(style);

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

      renderWindowInteractor->Start();

      return EXIT_SUCCESS;
    }

### CMakeLists.txt

    cmake_minimum_required(VERSION 2.8)

    PROJECT(ImageIdealHighPass)

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

    add_executable(ImageIdealHighPass MACOSX_BUNDLE ImageIdealHighPass.cxx )

    target_link_libraries(ImageIdealHighPass ${VTK_LIBRARIES})

### Download and Build ImageIdealHighPass

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

    cd ImageIdealHighPass/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:

    ./ImageIdealHighPass

WINDOWS USERS

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