Examples/Filtering/DerivativeImageFilter.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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 *         http://www.apache.org/licenses/LICENSE-2.0.txt
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 *  distributed under the License is distributed on an "AS IS" BASIS,
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 *  See the License for the specific language governing permissions and
 *  limitations under the License.
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//  Software Guide : BeginCommandLineArgs
//    INPUTS:  {BrainProtonDensitySlice.png}
//    ARGUMENTS: {DerivativeImageFilterFloatOutput.mhd}
//    OUTPUTS: {DerivativeImageFilterOutput.png}
//    ARGUMENTS:    1 0
//  Software Guide : EndCommandLineArgs
 
//  Software Guide : BeginLatex
//
//  The \doxygen{DerivativeImageFilter} is used for computing the partial
//  derivative of an image, the derivative of an image along a particular
//  axial direction.
//
//  \index{itk::DerivativeImageFilter}
//
//  Software Guide : EndLatex
 
 
#include "itkImage.h"
#include "itkImageFileReader.h"
#include "itkImageFileWriter.h"
#include "itkRescaleIntensityImageFilter.h"
 
//  Software Guide : BeginLatex
//
//  The header file corresponding to this filter should be included first.
//
//  \index{itk::DerivativeImageFilter!header}
//
//  Software Guide : EndLatex
 
 
// Software Guide : BeginCodeSnippet
#include "itkDerivativeImageFilter.h"
// Software Guide : EndCodeSnippet
 
 
int
main(int argc, char * argv[])
{
  if (argc < 6)
  {
    std::cerr << "Usage: " << std::endl;
    std::cerr
      << argv[0]
      << "  inputImageFile   outputImageFile  normalizedOutputImageFile ";
    std::cerr << " derivativeOrder direction" << std::endl;
    return EXIT_FAILURE;
  }
 
 
  //  Software Guide : BeginLatex
  //
  //  Next, the pixel types for the input and output images must be defined
  //  and, with them, the image types can be instantiated. Note that it is
  //  important to select a signed type for the image, since the values of the
  //  derivatives will be positive as well as negative.
  //
  //  Software Guide : EndLatex
 
  // Software Guide : BeginCodeSnippet
  using InputPixelType = float;
  using OutputPixelType = float;
 
  constexpr unsigned int Dimension = 2;
 
  using InputImageType = itk::Image<InputPixelType, Dimension>;
  using OutputImageType = itk::Image<OutputPixelType, Dimension>;
  // 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 define the filter type
  //  and create the filter object.
  //
  //  \index{itk::DerivativeImageFilter!instantiation}
  //  \index{itk::DerivativeImageFilter!New()}
  //  \index{itk::DerivativeImageFilter!Pointer}
  //
  //  Software Guide : EndLatex
 
  // Software Guide : BeginCodeSnippet
  using FilterType =
    itk::DerivativeImageFilter<InputImageType, OutputImageType>;
 
  FilterType::Pointer filter = FilterType::New();
  // Software Guide : EndCodeSnippet
 
 
  //  Software Guide : BeginLatex
  //
  //  The order of the derivative is selected with the \code{SetOrder()}
  //  method.  The direction along which the derivative will be computed is
  //  selected with the \code{SetDirection()} method.
  //
  //  \index{itk::DerivativeImageFilter!SetOrder()}
  //  \index{itk::DerivativeImageFilter!SetDirection()}
  //
  //  Software Guide : EndLatex
 
  // Software Guide : BeginCodeSnippet
  filter->SetOrder(std::stoi(argv[4]));
  filter->SetDirection(std::stoi(argv[5]));
  // 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 \code{Update()} call on any downstream filter
  //  will trigger the execution of the derivative filter.
  //
  //  \index{itk::DerivativeImageFilter!SetInput()}
  //  \index{itk::DerivativeImageFilter!GetOutput()}
  //
  //  Software Guide : EndLatex
 
 
  // Software Guide : BeginCodeSnippet
  filter->SetInput(reader->GetOutput());
  writer->SetInput(filter->GetOutput());
  writer->Update();
  // Software Guide : EndCodeSnippet
 
 
  //  Software Guide : BeginLatex
  //
  // \begin{figure}
  // \center
  // \includegraphics[width=0.44\textwidth]{BrainProtonDensitySlice}
  // \includegraphics[width=0.44\textwidth]{DerivativeImageFilterOutput}
  // \itkcaption[Effect of the Derivative filter.]{Effect of the Derivative
  // filter on a slice from a MRI proton density brain image.}
  // \label{fig:DerivativeImageFilterOutput}
  // \end{figure}
  //
  //  Figure \ref{fig:DerivativeImageFilterOutput} illustrates the effect of
  //  the DerivativeImageFilter on a slice of MRI brain image. The derivative
  //  is taken along the $x$ direction.  The sensitivity to noise in the image
  //  is evident from this result.
  //
  //  Software Guide : EndLatex
 
 
  using WriteImageType = itk::Image<unsigned char, Dimension>;
 
  using NormalizeFilterType =
    itk::RescaleIntensityImageFilter<OutputImageType, WriteImageType>;
 
  using NormalizedWriterType = itk::ImageFileWriter<WriteImageType>;
 
  NormalizeFilterType::Pointer  normalizer = NormalizeFilterType::New();
  NormalizedWriterType::Pointer normalizedWriter =
    NormalizedWriterType::New();
 
  normalizer->SetInput(filter->GetOutput());
  normalizedWriter->SetInput(normalizer->GetOutput());
 
  normalizer->SetOutputMinimum(0);
  normalizer->SetOutputMaximum(255);
 
  normalizedWriter->SetFileName(argv[3]);
  normalizedWriter->Update();
 
  return EXIT_SUCCESS;
}