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VTKSpectrum

Repository source: VTKSpectrum

Description

The discrete Fourier transform changes an image from the spatial domain into the frequency domain, where each pixel represents a sinusoidal function. This example shows an image and its power spectrum displayed using a logarithmic transfer function.

Info

See Figure 10-10 in Chapter 10 the VTK Textbook.

Other languages

See (Python), (PythonicAPI)

Question

If you have a question about this example, please use the VTK Discourse Forum

Code

VTKSpectrum.cxx

#include <vtkImageActor.h>
#include <vtkImageData.h>
#include <vtkImageFFT.h>
#include <vtkImageFourierCenter.h>
#include <vtkImageLogarithmicScale.h>
#include <vtkImageMagnitude.h>
#include <vtkImageMapToColors.h>
#include <vtkImageMapper3D.h>
#include <vtkImageProperty.h>
#include <vtkImageReader2.h>
#include <vtkImageReader2Factory.h>
#include <vtkInteractorStyleImage.h>
#include <vtkNamedColors.h>
#include <vtkNew.h>
#include <vtkRenderWindow.h>
#include <vtkRenderWindowInteractor.h>
#include <vtkRenderer.h>
#include <vtkSmartPointer.h>
#include <vtkWindowLevelLookupTable.h>

namespace {

void CreateImageActor(vtkImageActor* actor, double colorWindow,
                      double colorLevel);
}

int main(int argc, char* argv[])
{
  // Verify input arguments
  if (argc != 2)
  {
    std::cout << "Usage: " << argv[0] << " Filename e.g. vtks.pgm" << std::endl;
    return EXIT_FAILURE;
  }

  // Read the image
  vtkNew<vtkImageReader2Factory> readerFactory;
  vtkSmartPointer<vtkImageReader2> reader;
  reader.TakeReference(readerFactory->CreateImageReader2(argv[1]));
  reader->SetFileName(argv[1]);
  reader->Update();

  vtkNew<vtkImageFFT> fft;
  //  fft->SetFilteredAxes $VTK_IMAGE_X_AXIS $VTK_IMAGE_Y_AXIS
  fft->SetInputConnection(reader->GetOutputPort());

  vtkNew<vtkImageMagnitude> mag;
  mag->SetInputConnection(fft->GetOutputPort());

  vtkNew<vtkImageFourierCenter> center;
  center->SetInputConnection(mag->GetOutputPort());

  vtkNew<vtkImageLogarithmicScale> compress;
  compress->SetInputConnection(center->GetOutputPort());
  compress->SetConstant(15);
  compress->Update();

  // Create actors
  vtkNew<vtkNamedColors> colors;

  vtkNew<vtkImageActor> originalActor;
  originalActor->GetMapper()->SetInputConnection(reader->GetOutputPort());
  originalActor->GetProperty()->SetInterpolationTypeToNearest();

  vtkNew<vtkImageActor> compressedActor;
  compressedActor->GetMapper()->SetInputConnection(compress->GetOutputPort());
  compressedActor->GetProperty()->SetInterpolationTypeToNearest();
  CreateImageActor(compressedActor, 160, 120);

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

  // Setup renderers
  vtkNew<vtkRenderer> originalRenderer;
  originalRenderer->SetViewport(originalViewport);
  originalRenderer->AddActor(originalActor);
  originalRenderer->ResetCamera();
  originalRenderer->SetBackground(colors->GetColor3d("SlateGray").GetData());

  vtkNew<vtkRenderer> compressedRenderer;
  compressedRenderer->SetViewport(compressedViewport);
  compressedRenderer->AddActor(compressedActor);
  compressedRenderer->ResetCamera();
  compressedRenderer->SetBackground(
      colors->GetColor3d("LightSlateGray").GetData());

  vtkNew<vtkRenderWindow> renderWindow;
  renderWindow->SetSize(600, 300);
  renderWindow->SetWindowName("VTKSpectrum");
  renderWindow->AddRenderer(originalRenderer);
  renderWindow->AddRenderer(compressedRenderer);

  vtkNew<vtkRenderWindowInteractor> renderWindowInteractor;
  vtkNew<vtkInteractorStyleImage> style;

  renderWindowInteractor->SetInteractorStyle(style);

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

  renderWindowInteractor->Start();

  return EXIT_SUCCESS;
}

namespace {

void CreateImageActor(vtkImageActor* actor, double colorWindow,
                      double colorLevel)
{
  vtkNew<vtkWindowLevelLookupTable> wlut;
  wlut->SetWindow(colorWindow);
  wlut->SetLevel(colorLevel);
  wlut->Build();

  // Map the image through the lookup table
  vtkNew<vtkImageMapToColors> color;
  color->SetLookupTable(wlut);
  color->SetInputData(actor->GetMapper()->GetInput());

  actor->GetMapper()->SetInputConnection(color->GetOutputPort());
  return;
}

} // namespace

CMakeLists.txt

cmake_minimum_required(VERSION 3.12 FATAL_ERROR)

project(VTKSpectrum)

find_package(VTK COMPONENTS 
  CommonColor
  CommonCore
  CommonDataModel
  IOImage
  ImagingCore
  ImagingFourier
  ImagingMath
  InteractionStyle
  RenderingContextOpenGL2
  RenderingCore
  RenderingFreeType
  RenderingGL2PSOpenGL2
  RenderingOpenGL2
)

if (NOT VTK_FOUND)
  message(FATAL_ERROR "VTKSpectrum: Unable to find the VTK build folder.")
endif()

# Prevent a "command line is too long" failure in Windows.
set(CMAKE_NINJA_FORCE_RESPONSE_FILE "ON" CACHE BOOL "Force Ninja to use response files.")
add_executable(VTKSpectrum MACOSX_BUNDLE VTKSpectrum.cxx )
  target_link_libraries(VTKSpectrum PRIVATE ${VTK_LIBRARIES}
)
# vtk_module_autoinit is needed
vtk_module_autoinit(
  TARGETS VTKSpectrum
  MODULES ${VTK_LIBRARIES}
)

Download and Build VTKSpectrum

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

cd VTKSpectrum/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:

./VTKSpectrum

WINDOWS USERS

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