Compute Median of Image at Pixel

Synopsis

Computes the median of an image at a pixil(in a regular neighborhood).

Results

input.png

Output:

Median at [10, 10] is 0

Code

C++

#include "itkImage.h"
#include "itkImageFileWriter.h"
#include "itkImageRegionIterator.h"
#include "itkMedianImageFunction.h"

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

void
CreateImage(UnsignedCharImageType::Pointer image);

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

  using MedianImageFunctionType = itk::MedianImageFunction<UnsignedCharImageType>;
  MedianImageFunctionType::Pointer medianImageFunction = MedianImageFunctionType::New();
  medianImageFunction->SetInputImage(image);

  itk::Index<2> index;
  index.Fill(10);
  std::cout << "Median at " << index << " is " << static_cast<int>(medianImageFunction->EvaluateAtIndex(index))
            << std::endl;
  return EXIT_SUCCESS;
}

void
CreateImage(UnsignedCharImageType::Pointer image)
{
  itk::Index<2> start;
  start.Fill(0);

  itk::Size<2> size;
  size.Fill(100);

  itk::ImageRegion<2> region(start, size);

  image->SetRegions(region);
  image->Allocate();
  image->FillBuffer(0);

  itk::ImageRegionIterator<UnsignedCharImageType> imageIterator(image, region);

  while (!imageIterator.IsAtEnd())
  {
    if (imageIterator.GetIndex()[0] >= 50 && imageIterator.GetIndex()[1] >= 50 && imageIterator.GetIndex()[0] <= 70 &&
        imageIterator.GetIndex()[1] <= 70)
    {
      imageIterator.Set(255);
    }

    ++imageIterator;
  }

  using WriterType = itk::ImageFileWriter<UnsignedCharImageType>;
  WriterType::Pointer writer = WriterType::New();
  writer->SetFileName("input.png");
  writer->SetInput(image);
  writer->Update();
}

Classes demonstrated

template<typename TInputImage, typename TCoordRep = float>
class MedianImageFunction : public itk::ImageFunction<TInputImage, TInputImage::PixelType, TCoordRep>

Calculate the median value in the neighborhood of a pixel.

Calculate the median pixel value over the standard 8, 26, etc. connected neighborhood. This calculation uses a ZeroFluxNeumannBoundaryCondition.

If called with a ContinuousIndex or Point, the calculation is performed at the nearest neighbor.

This class is templated over the input image type and the coordinate representation type (e.g. float or double ).

ITK Sphinx Examples:

• All ITK Sphinx Examples

• Compute Median Of Image At Pixel

See itk::MedianImageFunction for additional documentation.