Process Nth Component of Vector Image

Synopsis

Process the nth component/element/channel of a vector image.

Results

Code

C++

#include "itkImageAdaptor.h"
#include "itkImageRegionIterator.h"
#include "itkNthElementImageAdaptor.h"
#include "itkBinomialBlurImageFilter.h"

using VectorImageType = itk::Image<itk::CovariantVector<float, 3>, 2>;

static void
CreateImage(VectorImageType::Pointer image);

int
main(int, char *[])
{
  VectorImageType::Pointer image = VectorImageType::New();
  CreateImage(image);

  using ImageAdaptorType = itk::NthElementImageAdaptor<VectorImageType, float>;

  ImageAdaptorType::Pointer adaptor = ImageAdaptorType::New();

  adaptor->SelectNthElement(0);
  adaptor->SetImage(image);

  using BlurFilterType = itk::BinomialBlurImageFilter<ImageAdaptorType, itk::Image<float, 2>>;
  BlurFilterType::Pointer blurFilter = BlurFilterType::New();
  blurFilter->SetInput(adaptor);
  blurFilter->Update();

  return EXIT_SUCCESS;
}

void
CreateImage(VectorImageType::Pointer image)
{
  VectorImageType::IndexType start;
  start.Fill(0);

  VectorImageType::SizeType size;
  size.Fill(2);

  VectorImageType::RegionType region;
  region.SetSize(size);
  region.SetIndex(start);

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

  itk::ImageRegionIterator<VectorImageType> imageIterator(image, image->GetLargestPossibleRegion());
  itk::CovariantVector<float, 3>            vec;
  vec[0] = 1;
  vec[1] = 2;
  vec[2] = 3;

  while (!imageIterator.IsAtEnd())
  {
    imageIterator.Set(vec);

    ++imageIterator;
  }
}

Classes demonstrated

template<typename TImage, typename TOutputPixelType>
class NthElementImageAdaptor : public itk::ImageAdaptor<TImage, PixelAccessor>

Presents an image as being composed of the N-th element of its pixels.

It assumes that the pixels are of container type and have in their API an operator[]( unsigned int ) defined.

Additional casting is performed according to the input and output image types following C++ default casting rules.

ITK Sphinx Examples:

See itk::NthElementImageAdaptor for additional documentation.