ITK/Examples/Iterators/ConstantBoundaryCondition

At the boundaries of an image, a NeighborhoodIterator will point to invalid pixels. This example demonstrates one method of handling these cases. It simply returns a specified constant value for any invalid pixel.

ConstantBoundaryCondition.cxx

<source lang="cpp">

1. include "itkImage.h"
2. include "itkImageFileReader.h"
3. include "itkConstNeighborhoodIterator.h"
4. include "itkConstantBoundaryCondition.h"
5. include "itkImageRegionIterator.h"

1. include <itkImageToVTKImageFilter.h>

1. include "vtkVersion.h"
2. include "vtkImageViewer.h"
3. include "vtkImageMapper3D.h"
4. include "vtkRenderWindowInteractor.h"
5. include "vtkSmartPointer.h"
6. include "vtkImageActor.h"
7. include "vtkInteractorStyleImage.h"
8. include "vtkRenderer.h"

typedef itk::Image<unsigned char, 2> ImageType; static void CreateImage(ImageType::Pointer image);

int main(int, char*[]) {

 ImageType::Pointer image = ImageType::New();
 CreateImage(image);
 
 ImageType::SizeType regionSize;
 regionSize[0] = 50;
 regionSize[1] = 1;

 ImageType::IndexType regionIndex;
 regionIndex[0] = 0;
 regionIndex[1] = 0;

 ImageType::RegionType region;
 region.SetSize(regionSize);
 region.SetIndex(regionIndex);

 ImageType::SizeType radius;
 radius[0] = 1;
 radius[1] = 1;

 typedef itk::ConstantBoundaryCondition<ImageType>  BoundaryConditionType;
 itk::ConstNeighborhoodIterator<ImageType, BoundaryConditionType> iterator(radius, image,region);

 while(!iterator.IsAtEnd())
   {
   for(unsigned int i = 0; i < 9; i++)
     {
     ImageType::IndexType index = iterator.GetIndex(i);

     std::cout << "Index: " << index
               << " Pixel: " << i << " = "
               << (int)iterator.GetPixel(i) << std::endl;
     }
   ++iterator;
   }

 // Visualize
 typedef itk::ImageToVTKImageFilter<ImageType> ConnectorType;
 ConnectorType::Pointer connector = ConnectorType::New();
 connector->SetInput(image);

 vtkSmartPointer<vtkImageActor> actor =
   vtkSmartPointer<vtkImageActor>::New();

1. if VTK_MAJOR_VERSION <= 5

 actor->SetInput(connector->GetOutput());

1. else

 connector->Update();
 actor->GetMapper()->SetInputData(connector->GetOutput());

1. endif

 vtkSmartPointer<vtkRenderWindow> renderWindow =
   vtkSmartPointer<vtkRenderWindow>::New();

 vtkSmartPointer<vtkRenderWindowInteractor> interactor =
   vtkSmartPointer<vtkRenderWindowInteractor>::New();
 interactor->SetRenderWindow(renderWindow);

 vtkSmartPointer<vtkRenderer> renderer =
   vtkSmartPointer<vtkRenderer>::New();
 renderWindow->AddRenderer(renderer);

 renderer->AddActor(actor);
 renderer->ResetCamera();

 renderWindow->Render();

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

 interactor->SetInteractorStyle(style);

 interactor->Start();

 return EXIT_SUCCESS;

}

void CreateImage(ImageType::Pointer image) {

 // Create an image with 2 connected components
 ImageType::RegionType region;
 ImageType::IndexType start;
 start[0] = 0;
 start[1] = 0;

 ImageType::SizeType size;
 unsigned int NumRows = 5;
 unsigned int NumCols = 5;
 size[0] = NumRows;
 size[1] = NumCols;

 region.SetSize(size);
 region.SetIndex(start);

 image->SetRegions(region);
 image->Allocate();

 itk::ImageRegionIterator<ImageType> imageIterator(image,region);

 // Set all pixels to white
 while(!imageIterator.IsAtEnd())
   {
   imageIterator.Set(255);
   ++imageIterator;
   }

} </source>

CMakeLists.txt

<syntaxhighlight lang="cmake"> cmake_minimum_required(VERSION 3.9.5)

project(ConstantBoundaryCondition)

find_package(ITK REQUIRED) include(${ITK_USE_FILE}) if (ITKVtkGlue_LOADED)

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

else()

 find_package(ItkVtkGlue REQUIRED)
 include(${ItkVtkGlue_USE_FILE})
 set(Glue ItkVtkGlue)

endif()

add_executable(ConstantBoundaryCondition MACOSX_BUNDLE ConstantBoundaryCondition.cxx) target_link_libraries(ConstantBoundaryCondition

 ${Glue}  ${VTK_LIBRARIES} ${ITK_LIBRARIES})

</syntaxhighlight>

Download and Build ConstantBoundaryCondition

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

cd ConstantBoundaryCondition/build 

• If ITK is installed:

cmake ..

• If ITK is not installed but compiled on your system, you will need to specify the path to your ITK build:

cmake -DITK_DIR:PATH=/home/me/itk_build ..

Build the project,

make

and run it:

./ConstantBoundaryCondition

WINDOWS USERS PLEASE NOTE: Be sure to add the VTK and ITK bin directories to your path. This will resolve the VTK and ITK dll's at run time.

Building All of the Examples

Many of the examples in the ITK Wiki Examples Collection require VTK. You can build all of the the examples by following these instructions. If you are a new VTK user, you may want to try the Superbuild which will build a proper ITK and VTK.

ItkVtkGlue

ITK >= 4

For examples that use QuickView (which depends on VTK), you must have built ITK with Module_ITKVtkGlue=ON.

ITK < 4

Some of the ITK Examples require VTK to display the images. If you download the entire ITK Wiki Examples Collection, the ItkVtkGlue directory will be included and configured. If you wish to just build a few examples, then you will need to download ItkVtkGlue and build it. When you run cmake it will ask you to specify the location of the ItkVtkGlue binary directory.