Examples/Filtering/OtsuThresholdImageFilter.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
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 *         https://www.apache.org/licenses/LICENSE-2.0.txt
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//  Software Guide : BeginCommandLineArgs
//    INPUTS:  {BrainProtonDensitySlice.png}
//    OUTPUTS: {OtsuThresholdImageFilterOutput.png}
//    ARGUMENTS:    255 0
//  Software Guide : EndCommandLineArgs
 
// Software Guide : BeginLatex
//
// This example illustrates how to use the \doxygen{OtsuThresholdImageFilter}.
//
// Software Guide : EndLatex
 
// Software Guide : BeginCodeSnippet
#include "itkOtsuThresholdImageFilter.h"
// Software Guide : EndCodeSnippet
 
#include "itkImage.h"
#include "itkImageFileReader.h"
#include "itkImageFileWriter.h"
 
int
main(int argc, char * argv[])
{
  if (argc < 5)
  {
    std::cerr << "Usage: " << argv[0];
    std::cerr << " inputImageFile outputImageFile ";
    std::cerr << " insideValue    outsideValue   " << std::endl;
    return EXIT_FAILURE;
  }
 
  //  Software Guide : BeginLatex
  //
  //  The next step is to decide which pixel types to use for the input and
  //  output images, and to define the image dimension.
  //
  //  Software Guide : EndLatex
 
  // Software Guide : BeginCodeSnippet
  using InputPixelType = unsigned char;
  using OutputPixelType = unsigned char;
  constexpr unsigned int Dimension = 2;
  // Software Guide : EndCodeSnippet
 
 
  //  Software Guide : BeginLatex
  //
  //  The input and output image types are now defined using their respective
  //  pixel types and dimensions.
  //
  //  Software Guide : EndLatex
 
  // Software Guide : BeginCodeSnippet
  using InputImageType = itk::Image<InputPixelType, Dimension>;
  using OutputImageType = itk::Image<OutputPixelType, Dimension>;
  // Software Guide : EndCodeSnippet
 
 
  //  Software Guide : BeginLatex
  //
  //  The filter type can be instantiated using the input and output image
  //  types defined above.
  //
  //  Software Guide : EndLatex
 
  // Software Guide : BeginCodeSnippet
  using FilterType =
    itk::OtsuThresholdImageFilter<InputImageType, OutputImageType>;
  // Software Guide : EndCodeSnippet
 
 
  //  Software Guide : BeginLatex
  //
  //  An \doxygen{ImageFileReader} class is also instantiated in order to read
  //  image data from a file. (See Section \ref{sec:IO} on page
  //  \pageref{sec:IO} for more information about reading
  //  and writing data.)
  //
  //  Software Guide : EndLatex
 
  // Software Guide : BeginCodeSnippet
  using ReaderType = itk::ImageFileReader<InputImageType>;
  // Software Guide : EndCodeSnippet
 
 
  //  Software Guide : BeginLatex
  //
  // An \doxygen{ImageFileWriter} is instantiated in order to write the output
  // image to a file.
  //
  //  Software Guide : EndLatex
 
 
  // Software Guide : BeginCodeSnippet
  using WriterType = itk::ImageFileWriter<OutputImageType>;
  // Software Guide : EndCodeSnippet
 
 
  //  Software Guide : BeginLatex
  //
  //  Both the filter and the reader are created by invoking their
  //  \code{New()} methods and assigning the result to
  //  \doxygen{SmartPointer}s.
  //
  //  Software Guide : EndLatex
 
  // Software Guide : BeginCodeSnippet
  auto reader = ReaderType::New();
  auto filter = FilterType::New();
  // Software Guide : EndCodeSnippet
 
  auto writer = WriterType::New();
  writer->SetInput(filter->GetOutput());
  reader->SetFileName(argv[1]);
 
 
  //  Software Guide : BeginLatex
  //
  //  The image obtained with the reader is passed as input to the
  //  \code{OtsuThresholdImageFilter}.
  //
  //  \index{itk::Otsu\-Threshold\-Image\-Filter!SetInput()}
  //  \index{itk::FileImageReader!GetOutput()}
  //
  //  Software Guide : EndLatex
 
  // Software Guide : BeginCodeSnippet
  filter->SetInput(reader->GetOutput());
  // Software Guide : EndCodeSnippet
 
 
  //  Software Guide : BeginLatex
  //
  //  The method \code{SetOutsideValue()} defines the intensity value to be
  //  assigned to those pixels whose intensities are outside the range defined
  //  by the lower and upper thresholds. The method \code{SetInsideValue()}
  //  defines the intensity value to be assigned to pixels with intensities
  //  falling inside the threshold range.
  //
  //  \index{itk::Otsu\-Threshold\-Image\-Filter!SetOutsideValue()}
  //  \index{itk::Otsu\-Threshold\-Image\-Filter!SetInsideValue()}
  //  \index{SetOutsideValue()!itk::Otsu\-Threshold\-Image\-Filter}
  //  \index{SetInsideValue()!itk::Otsu\-Threshold\-Image\-Filter}
  //
  //  Software Guide : EndLatex
 
  const OutputPixelType outsideValue = std::stoi(argv[3]);
  const OutputPixelType insideValue = std::stoi(argv[4]);
 
  // Software Guide : BeginCodeSnippet
  filter->SetOutsideValue(outsideValue);
  filter->SetInsideValue(insideValue);
  // Software Guide : EndCodeSnippet
 
 
  //  Software Guide : BeginLatex
  //
  //  Execution of the filter is triggered by invoking the \code{Update()}
  //  method, which we wrap in a \code{try/catch} block.  If the filter's
  //  output has been passed as input to subsequent filters, the
  //  \code{Update()} call on any downstream filters in the pipeline will
  //  indirectly trigger the update of this filter.
  //
  //  Software Guide : EndLatex
 
  // Software Guide : BeginCodeSnippet
  try
  {
    filter->Update();
  }
  catch (const itk::ExceptionObject & excp)
  {
    std::cerr << "Exception thrown " << excp << std::endl;
  }
  // Software Guide : EndCodeSnippet
 
 
  //  Software Guide : BeginLatex
  //
  //  We can now retrieve the internally-computed threshold value with the
  //  \code{GetThreshold()} method and print it to the console.
  //
  //  Software Guide : EndLatex
 
  // Software Guide : BeginCodeSnippet
  const int threshold = filter->GetThreshold();
  std::cout << "Threshold = " << threshold << std::endl;
  // Software Guide : EndCodeSnippet
 
 
  //  Software Guide : BeginLatex
  //
  // \begin{figure}
  // \center
  // \includegraphics[width=0.44\textwidth]{BrainProtonDensitySlice}
  // \includegraphics[width=0.44\textwidth]{OtsuThresholdImageFilterOutput}
  // \itkcaption[OtsuThresholdImageFilter output]{Effect of the
  // OtsuThresholdImageFilter on a slice from a MRI proton density image  of
  // the brain.}
  // \label{fig:OtsuThresholdImageFilterInputOutput}
  // \end{figure}
  //
  //  Figure \ref{fig:OtsuThresholdImageFilterInputOutput} illustrates the
  //  effect of this filter on a MRI proton density image of the brain. This
  //  figure shows the limitations of this filter for performing segmentation
  //  by itself. These limitations are particularly noticeable in noisy images
  //  and in images lacking spatial uniformity as is the case with MRI due to
  //  field bias.
  //
  //  \relatedClasses
  //  \begin{itemize}
  //  \item \doxygen{ThresholdImageFilter}
  //  \end{itemize}
  //
  //  Software Guide : EndLatex
 
  writer->SetFileName(argv[2]);
  try
  {
    writer->Update();
  }
  catch (const itk::ExceptionObject & excp)
  {
    std::cerr << "Exception thrown " << excp << std::endl;
  }
 
  return EXIT_SUCCESS;
}