Custom Operation to Corresponding Pixels in Two Images#

Synopsis#

Apply a predefined operation to corresponding pixels in two images.

Results#

Output:

pixel1 was = 2
pixel2 was = 5
output is = 9

Code#

C++#

#include "itkVectorImage.h"
#include "itkVector.h"
#include "itkVariableLengthVector.h"
#include "itkRigid2DTransform.h"
#include "itkBinaryFunctorImageFilter.h"

using ImageType = itk::Image<float, 2>;
static void
CreateImage(ImageType::Pointer image);

namespace Functor
{
template <class TPixel>
class MySquaredDifference
{
public:
  MySquaredDifference() = default;
  ~MySquaredDifference() = default;
  bool
  operator!=(const MySquaredDifference &) const
  {
    return false;
  }

  bool
  operator==(const MySquaredDifference & other) const
  {
    return !(*this != other);
  }

  inline TPixel
  operator()(const TPixel & A, const TPixel & B) const
  {
    const auto   dA = static_cast<double>(A);
    const auto   dB = static_cast<double>(B);
    const double diff = dA - dB;

    return static_cast<TPixel>(diff * diff);
  }
};
} // namespace Functor

int
main()
{
  auto image1 = ImageType::New();
  CreateImage(image1);
  image1->FillBuffer(2);

  auto image2 = ImageType::New();
  CreateImage(image2);
  image2->FillBuffer(5);

  using FilterType =
    itk::BinaryFunctorImageFilter<ImageType, ImageType, ImageType, Functor::MySquaredDifference<ImageType::PixelType>>;

  auto filter = FilterType::New();
  filter->SetInput1(image1);
  filter->SetInput2(image2);
  filter->Update();

  itk::Index<2> pixelIndex{};

  ImageType::PixelType input1PixelValue = image1->GetPixel(pixelIndex);
  ImageType::PixelType input2PixelValue = image2->GetPixel(pixelIndex);
  ImageType::PixelType outputPixelValue = filter->GetOutput()->GetPixel(pixelIndex);

  std::cout << "pixel1 was = " << input1PixelValue << std::endl;
  std::cout << "pixel2 was = " << input2PixelValue << std::endl;
  std::cout << "output is = " << outputPixelValue << std::endl;

  return EXIT_SUCCESS;
}

void
CreateImage(ImageType::Pointer image)
{
  ImageType::IndexType start{};

  auto size = ImageType::SizeType::Filled(10);

  ImageType::RegionType region(start, size);
  image->SetRegions(region);
  image->Allocate();
}

Classes demonstrated#

template<typename TInputImage1, typename TInputImage2, typename TOutputImage, typename TFunction> class BinaryFunctorImageFilter : public itk::InPlaceImageFilter<TInputImage1, TOutputImage>

Implements pixel-wise generic operation of two images, or of an image and a constant.

This class is parameterized over the types of the two input images and the type of the output image. It is also parameterized by the operation to be applied. A Functor style is used.

The constant must be of the same type than the pixel type of the corresponding image. It is wrapped in a SimpleDataObjectDecorator so it can be updated through the pipeline. The SetConstant() and GetConstant() methods are provided as shortcuts to set or get the constant value without manipulating the decorator.