Examples/Segmentation/RelabelComponentImageFilter.cxx

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 *
 *  Copyright NumFOCUS
 *
 *  Licensed under the Apache License, Version 2.0 (the "License");
 *  you may not use this file except in compliance with the License.
 *  You may obtain a copy of the License at
 *
 *         https://www.apache.org/licenses/LICENSE-2.0.txt
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 *  distributed under the License is distributed on an "AS IS" BASIS,
 *  WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 *  See the License for the specific language governing permissions and
 *  limitations under 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>;
 
  auto reader = ReaderType::New();
  auto 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>;
 
  auto 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;
}