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Add Constant to Every Pixel Without Duplicating Memory

Synopsis

Add a constant to every pixel without duplicating the image in memory (an accessor).

Results

Output:

addPixelAccessor.SetValue(5)
image->GetPixel[0, 0]: 20 adaptor->GetPixel[0, 0]: 25
addPixelAccessor.SetValue(100)
image->GetPixel[0, 0]: 20 adaptor->GetPixel[0, 0]: 120

Code

C++

#include "itkImage.h"
#include "itkAddPixelAccessor.h"
#include "itkImageAdaptor.h"
#include "itkImageRegionIterator.h"

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

static void
CreateImage(ImageType::Pointer image);

int
main()
{
  auto image = ImageType::New();
  CreateImage(image);

  using AddPixelAccessorType = itk::Accessor::AddPixelAccessor<ImageType::PixelType>;
  using ImageAdaptorType = itk::ImageAdaptor<ImageType, AddPixelAccessorType>;

  auto                 adaptor = ImageAdaptorType::New();
  AddPixelAccessorType addPixelAccessor;


  adaptor->SetImage(image);

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

  addPixelAccessor.SetValue(5);
  adaptor->SetPixelAccessor(addPixelAccessor);
  std::cout << "addPixelAccessor.SetValue(5)" << std::endl;
  std::cout << "\timage->GetPixel" << index << ": " << image->GetPixel(index) << " adaptor->GetPixel" << index << ": "
            << adaptor->GetPixel(index) << std::endl;

  addPixelAccessor.SetValue(100);
  adaptor->SetPixelAccessor(addPixelAccessor);
  std::cout << "addPixelAccessor.SetValue(100)" << std::endl;
  std::cout << "\timage->GetPixel" << index << ": " << image->GetPixel(index) << " adaptor->GetPixel" << index << ": "
            << adaptor->GetPixel(index) << std::endl;

  return EXIT_SUCCESS;
}

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

  ImageType::SizeType size;
  size.Fill(10);

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

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

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

  while (!imageIterator.IsAtEnd())
  {
    imageIterator.Set(20);
    ++imageIterator;
  }
}

Classes demonstrated

template<typename TPixel>
class AddPixelAccessor

Simulates the effect of adding a constant value to all pixels.

This class is intended to be used as parameter of an ImageAdaptor to make an image appear as having pixels with intensity values increased by a constant amount.

See

ImageAdaptor

ITK Sphinx Examples:

• All ITK Sphinx Examples

• Add Constant To Every Pixel Without Duplicating Memory

See itk::Accessor::AddPixelAccessor for additional documentation.