Examples/Segmentation/RelabelComponentImageFilter.cxx

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 *  Licensed under the Apache License, Version 2.0 (the "License");
 *  you may not use this file except in compliance with the License.
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//  Software Guide : BeginLatex
//
//  The \doxygen{RelabelComponentImageFilter} is commonly used for reorganizing
//  the labels in an image that has been produced as the result of a
//  segmentation method. For example, region growing, or a K-means statistical
//  classification.
//
//  \index{itk::RelabelComponentImageFilter}
//
//  Software Guide : EndLatex


#include "itkImageFileReader.h"
#include "itkImageFileWriter.h"

//  Software Guide : BeginLatex
//
//  The header file corresponding to this filter should be included first.
//
//  \index{itk::RelabelComponentImageFilter!header}
//
//  Software Guide : EndLatex


// Software Guide : BeginCodeSnippet
#include "itkRelabelComponentImageFilter.h"
// Software Guide : EndCodeSnippet


int main( int argc, char * argv[] )
{
  if( argc < 3 )
    {
    std::cerr << "Usage: " << std::endl;
    std::cerr << argv[0] << " inputImageFile outputImageFile" << std::endl;
    return EXIT_FAILURE;
    }


  //  Software Guide : BeginLatex
  //
  //  Then the pixel types for input and output image must be defined and, with
  //  them, the image types can be instantiated.
  //
  //  Software Guide : EndLatex

  // Software Guide : BeginCodeSnippet
  using InputPixelType = unsigned char;
  using OutputPixelType = unsigned char;

  using InputImageType = itk::Image< InputPixelType,  2 >;
  using OutputImageType = itk::Image< OutputPixelType, 2 >;
  // Software Guide : EndCodeSnippet


  using ReaderType = itk::ImageFileReader< InputImageType  >;
  using WriterType = itk::ImageFileWriter< OutputImageType >;

  ReaderType::Pointer reader = ReaderType::New();
  WriterType::Pointer writer = WriterType::New();

  reader->SetFileName( argv[1] );
  writer->SetFileName( argv[2] );

  //  Software Guide : BeginLatex
  //
  //  Using the image types it is now possible to instantiate the filter type
  //  and create the filter object.
  //
  //  \index{itk::RelabelComponentImageFilter!instantiation}
  //  \index{itk::RelabelComponentImageFilter!New()}
  //  \index{itk::RelabelComponentImageFilter!Pointer}
  //
  //  Software Guide : EndLatex

  // Software Guide : BeginCodeSnippet
  using FilterType = itk::RelabelComponentImageFilter<
               InputImageType, OutputImageType >;

  FilterType::Pointer relabeler = FilterType::New();
  // Software Guide : EndCodeSnippet


  //  Software Guide : BeginLatex
  //
  //  The input to the filter can be taken from any other filter, for example
  //  a reader. The output can be passed down the pipeline to other filters,
  //  for example, a writer. An update call on any downstream filter will
  //  trigger the execution of the mean filter.
  //
  //  \index{itk::RelabelComponentImageFilter!SetInput()}
  //  \index{itk::RelabelComponentImageFilter!GetOutput()}
  //
  //  Software Guide : EndLatex


  // Software Guide : BeginCodeSnippet
  relabeler->SetInput( reader->GetOutput() );
  writer->SetInput( relabeler->GetOutput() );
  writer->Update();
  // Software Guide : EndCodeSnippet


  // Software Guide : BeginLatex
  //
  // We can now query the size of each one of the connected components, both in
  // pixel units and in physical units.
  //
  // Software Guide : EndLatex

  // Software Guide : BeginCodeSnippet
  using SizesInPixelsType = std::vector< itk::SizeValueType >;
  const SizesInPixelsType & sizesInPixels
                                      = relabeler->GetSizeOfObjectsInPixels();

  auto sizeItr = sizesInPixels.begin();
  auto sizeEnd = sizesInPixels.end();
  std::cout << "Number of pixels per class " << std::endl;
  unsigned int kclass = 0;
  while (sizeItr != sizeEnd)
    {
    std::cout << "Class " << kclass << " = " << *sizeItr << std::endl;
    ++kclass;
    ++sizeItr;
    }
  // Software Guide : EndCodeSnippet

  // Software Guide : BeginCodeSnippet
  using SizesInPhysicalUnitsType = std::vector< float >;
  const SizesInPhysicalUnitsType sizesInUnits
                               = relabeler->GetSizeOfObjectsInPhysicalUnits();

  auto physicalSizeItr = sizesInUnits.begin();
  auto physicalSizeEnd = sizesInUnits.end();

  std::cout << "Area in Physical Units per class " << std::endl;
  unsigned int jclass = 0;
  while( physicalSizeItr != physicalSizeEnd )
    {
    std::cout << "Class " << jclass << " = " << *physicalSizeItr << std::endl;
    ++jclass;
    ++physicalSizeItr;
    }
  // Software Guide : EndCodeSnippet

  return EXIT_SUCCESS;
}