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.

Info

See this figure in Chapter 10 the VTK Textbook.

Other languages

See (Python)

Question

If you have a simple question about this example contact us at VTKExProject If your question is more complex and may require extended discussion, please use the VTK Discourse Forum

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 
  vtkvtkCommonColor
  vtkvtkCommonCore
  vtkvtkCommonDataModel
  vtkvtkIOImage
  vtkvtkImagingCore
  vtkvtkImagingGeneral
  vtkvtkImagingSources
  vtkvtkInteractionStyle
  vtkvtkRenderingContextOpenGL2
  vtkvtkRenderingCore
  vtkvtkRenderingFreeType
  vtkvtkRenderingGL2PSOpenGL2
  vtkvtkRenderingOpenGL2 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

WINDOWS USERS

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