Median Filtering of an RGB Image

Synopsis

Apply median filtering on a RGB Image. The sorting of pixel is performed on their luminance.

Results

Input image

Output image

Code

C++

#include "itkMedianImageFilter.h"

#include "itkRGBPixel.h"
#include "itkImage.h"
#include "itkImageFileReader.h"
#include "itkImageFileWriter.h"

namespace itk
{
/** \class myRGBPixel
 * \brief Extends RGBPixel with operator <=
 *
 * This class overrides the <= and < operators to use Luminance as a sorting
 * value.
 */
template <typename TComponent = unsigned short>
class myRGBPixel : public RGBPixel<TComponent>
{
public:
  using Self = myRGBPixel;
  using Superclass = RGBPixel<TComponent>;

  using RGBPixel<TComponent>::operator=;

  bool
  operator<=(const Self & r) const
  {
    return (this->GetLuminance() <= r.GetLuminance());
  }
  bool
  operator<(const Self & r) const
  {
    return (this->GetLuminance() < r.GetLuminance());
  }
};
} // namespace itk

int
main(int argc, char * argv[])
{
  // Verify command line arguments
  if (argc != 4)
  {
    std::cerr << "Usage: " << std::endl;
    std::cerr << argv[0] << " <InputImageFile> <OutputImageFile> <radius>" << std::endl;
    return EXIT_FAILURE;
  }

  // Setup types
  constexpr unsigned int Dimension = 2;

  using MyPixelType = itk::myRGBPixel<unsigned char>;
  using MyImageType = itk::Image<MyPixelType, Dimension>;

  // Create and setup a reader
  using ReaderType = itk::ImageFileReader<MyImageType>;
  ReaderType::Pointer reader = ReaderType::New();
  reader->SetFileName(argv[1]);

  // Create and setup a median filter
  using FilterType = itk::MedianImageFilter<MyImageType, MyImageType>;
  FilterType::Pointer medianFilter = FilterType::New();

  FilterType::InputSizeType radius;
  radius.Fill(std::stoi(argv[3]));

  medianFilter->SetRadius(radius);
  medianFilter->SetInput(reader->GetOutput());

  // Cast the custom myRBGPixel's to RGBPixel's
  using RGBPixelType = itk::RGBPixel<unsigned char>;
  using RGBImageType = itk::Image<RGBPixelType, Dimension>;
  using CastType = itk::CastImageFilter<MyImageType, RGBImageType>;
  CastType::Pointer cast = CastType::New();
  cast->SetInput(medianFilter->GetOutput());

  using WriterType = itk::ImageFileWriter<RGBImageType>;
  WriterType::Pointer writer = WriterType::New();
  writer->SetInput(cast->GetOutput());
  writer->SetFileName(argv[2]);

  try
  {
    writer->Update();
  }
  catch (itk::ExceptionObject & error)
  {
    std::cerr << "Error: " << error << std::endl;
    return EXIT_FAILURE;
  }

  return EXIT_SUCCESS;
}

Classes demonstrated

template<typename TInputImage, typename TOutputImage>
class MedianImageFilter : public itk::BoxImageFilter<TInputImage, TOutputImage>

Applies a median filter to an image.

Computes an image where a given pixel is the median value of the the pixels in a neighborhood about the corresponding input pixel.

A median filter is one of the family of nonlinear filters. It is used to smooth an image without being biased by outliers or shot noise.

This filter requires that the input pixel type provides an operator<() (LessThan Comparable).

See

Image

See

Neighborhood

See

NeighborhoodOperator

See

NeighborhoodIterator

ITK Sphinx Examples:

• All ITK Sphinx Examples

• Median Filter Of An Image

• Median Filter Of An RGB Image

See itk::MedianImageFilter for additional documentation.