GaussianSmooth

VTKEx/Cxx/ImageProcessing/GaussianSmooth

Description¶

Low-pass filters can be implemented as convolution with a Gaussian kernel. The Gaussian kernel displayed on top has been magnified for this figure.

Code¶

GaussianSmooth.cxx

#include <vtkImageActor.h>
#include <vtkImageCast.h>
#include <vtkImageData.h>
#include <vtkImageGaussianSmooth.h>
#include <vtkImageMapper3D.h>
#include <vtkImageNoiseSource.h>
#include <vtkImageReader2.h>
#include <vtkImageReader2Factory.h>
#include <vtkInteractorStyleImage.h>
#include <vtkInteractorStyleImage.h>
#include <vtkNamedColors.h>
#include <vtkRenderer.h>
#include <vtkRenderWindow.h>
#include <vtkRenderWindowInteractor.h>
#include <vtkSmartPointer.h>

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;
  reader.TakeReference(
    readerFactory->CreateImageReader2(argv[1]));
  reader->SetFileName(argv[1]);
  reader->Update();

  // Process the 
  vtkSmartPointer<vtkImageCast> cast =
    vtkSmartPointer<vtkImageCast>::New();
  cast->SetInputConnection(reader->GetOutputPort());
  cast->SetOutputScalarTypeToFloat();

  vtkSmartPointer<vtkImageGaussianSmooth> filter =
    vtkSmartPointer<vtkImageGaussianSmooth>::New();
  filter->SetDimensionality(2);
  filter->SetInputConnection(cast->GetOutputPort());
  filter->SetStandardDeviations(4.0, 4.0);
  filter->SetRadiusFactors(2.0, 2.0);

  // Create actors
  vtkSmartPointer<vtkNamedColors> colors =
    vtkSmartPointer<vtkNamedColors>::New();

  vtkSmartPointer<vtkImageActor> originalActor =
    vtkSmartPointer<vtkImageActor>::New();
  originalActor->GetMapper()->SetInputConnection(
    reader->GetOutputPort());

  vtkSmartPointer<vtkImageActor> filteredActor =
    vtkSmartPointer<vtkImageActor>::New();
  filteredActor->GetMapper()->SetInputConnection(
    filter->GetOutputPort());

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

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

  vtkSmartPointer<vtkRenderer> filteredRenderer =
    vtkSmartPointer<vtkRenderer>::New();
  filteredRenderer->SetViewport(filteredViewport);
  filteredRenderer->AddActor(filteredActor);
  filteredRenderer->ResetCamera();
  filteredRenderer->SetBackground(colors->GetColor3d("LightSlateGray").GetData());

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

  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(GaussianSmooth)

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

Download and Build GaussianSmooth¶

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

cd GaussianSmooth/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:

./GaussianSmooth