Make Out Of Bounds Pixels Return Constant Value

Synopsis

Make out of bounds pixels return a constant value.

Results

VTK Window

Output In VTK Window

Output:

Index: [-1, -1] Pixel: 0 = 0
Index: [0, -1] Pixel: 1 = 0
Index: [1, -1] Pixel: 2 = 0
Index: [-1, 0] Pixel: 3 = 0
Index: [0, 0] Pixel: 4 = 255
Index: [1, 0] Pixel: 5 = 255
Index: [-1, 1] Pixel: 6 = 0
Index: [0, 1] Pixel: 7 = 255
Index: [1, 1] Pixel: 8 = 255
Index: [0, -1] Pixel: 0 = 0
Index: [1, -1] Pixel: 1 = 0
Index: [2, -1] Pixel: 2 = 0
Index: [0, 0] Pixel: 3 = 255
Index: [1, 0] Pixel: 4 = 255
Index: [2, 0] Pixel: 5 = 255
Index: [0, 1] Pixel: 6 = 255
Index: [1, 1] Pixel: 7 = 255
Index: [2, 1] Pixel: 8 = 255
Index: [1, -1] Pixel: 0 = 0
Index: [2, -1] Pixel: 1 = 0
Index: [3, -1] Pixel: 2 = 0
Index: [1, 0] Pixel: 3 = 255
Index: [2, 0] Pixel: 4 = 255
Index: [3, 0] Pixel: 5 = 255
Index: [1, 1] Pixel: 6 = 255
Index: [2, 1] Pixel: 7 = 255
Index: [3, 1] Pixel: 8 = 255
Index: [2, -1] Pixel: 0 = 0
Index: [3, -1] Pixel: 1 = 0
Index: [4, -1] Pixel: 2 = 0
Index: [2, 0] Pixel: 3 = 255
Index: [3, 0] Pixel: 4 = 255
Index: [4, 0] Pixel: 5 = 255
Index: [2, 1] Pixel: 6 = 255
Index: [3, 1] Pixel: 7 = 255
Index: [4, 1] Pixel: 8 = 255
Index: [3, -1] Pixel: 0 = 0
Index: [4, -1] Pixel: 1 = 0
Index: [5, -1] Pixel: 2 = 0
Index: [3, 0] Pixel: 3 = 255
Index: [4, 0] Pixel: 4 = 255
Index: [5, 0] Pixel: 5 = 0
Index: [3, 1] Pixel: 6 = 255
Index: [4, 1] Pixel: 7 = 255
Index: [5, 1] Pixel: 8 = 0

Code

C++

#include "itkImage.h"
#include "itkImageFileReader.h"
#include "itkConstNeighborhoodIterator.h"
#include "itkConstantBoundaryCondition.h"
#include "itkImageRegionIterator.h"

#include <itkImageToVTKImageFilter.h>

#include "vtkVersion.h"
#include "vtkImageViewer.h"
#include "vtkImageMapper3D.h"
#include "vtkRenderWindowInteractor.h"
#include "vtkSmartPointer.h"
#include "vtkImageActor.h"
#include "vtkInteractorStyleImage.h"
#include "vtkRenderer.h"

using ImageType = itk::Image<unsigned char, 2>;
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;

  using BoundaryConditionType = itk::ConstantBoundaryCondition<ImageType>;
  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
  using ConnectorType = itk::ImageToVTKImageFilter<ImageType>;
  ConnectorType::Pointer connector = ConnectorType::New();
  connector->SetInput(image);

  vtkSmartPointer<vtkImageActor> actor = vtkSmartPointer<vtkImageActor>::New();
#if VTK_MAJOR_VERSION <= 5
  actor->SetInput(connector->GetOutput());
#else
  connector->Update();
  actor->GetMapper()->SetInputData(connector->GetOutput());
#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;
  }
}

Classes demonstrated