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), (PythonicAPI)

Question

If you have a question about this example, 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 <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>

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

  // Process the
  vtkNew<vtkImageCast> cast;
  cast->SetInputConnection(reader->GetOutputPort());
  cast->SetOutputScalarTypeToFloat();

  vtkNew<vtkImageGaussianSmooth> filter;
  filter->SetDimensionality(2);
  filter->SetInputConnection(cast->GetOutputPort());
  filter->SetStandardDeviations(4.0, 4.0);
  filter->SetRadiusFactors(2.0, 2.0);

  // Create actors
  vtkNew<vtkNamedColors> colors;

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

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

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

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

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

  renderWindowInteractor->SetInteractorStyle(style);

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

  renderWindowInteractor->Start();

  return EXIT_SUCCESS;
}

CMakeLists.txt¶

cmake_minimum_required(VERSION 3.12 FATAL_ERROR)

project(GaussianSmooth)

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

if (NOT VTK_FOUND)
  message(FATAL_ERROR "GaussianSmooth: 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(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}
)

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.