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 "vtkImageViewer.h"
2. include "vtkRenderWindowInteractor.h"
3. include "vtkSmartPointer.h"
4. include "vtkImageActor.h"
5. include "vtkInteractorStyleImage.h"
6. 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();
 actor->SetInput(connector->GetOutput());

 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

<source lang="cmake"> cmake_minimum_required(VERSION 2.6)

PROJECT(ConstantBoundaryCondition)

include_directories(/home/doriad/src/ITK/Wrapping/WrapITK/ExternalProjects/ItkVtkGlue/src/)

FIND_PACKAGE(VTK REQUIRED) INCLUDE(${VTK_USE_FILE})

FIND_PACKAGE(ITK REQUIRED) INCLUDE(${ITK_USE_FILE})

ADD_EXECUTABLE(ConstantBoundaryCondition ConstantBoundaryCondition.cxx) TARGET_LINK_LIBRARIES(ConstantBoundaryCondition vtkHybrid ITKNumerics ITKBasicFilters ITKCommon ITKIO)

</source>