Examples/Filtering/ZeroCrossingBasedEdgeDetectionImageFilter.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.
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//  Software Guide : BeginCommandLineArgs
//    INPUTS:  {BrainProtonDensitySlice.png}
//    OUTPUTS: {ZeroCrossingBasedEdgeDetectionImageFilter.png}
//    ARGUMENTS:    1.0  0.1
//  Software Guide : EndCommandLineArgs
//
//  Software Guide : BeginLatex
//
//  The \doxygen{ZeroCrossingBasedEdgeDetectionImageFilter} performs
//  edge detection by combining a sequence of Gaussian smoothing,
//  Laplacian filter, and Zero crossing detections on the Laplacian.
//
//  \index{itk::ZeroCrossingBasedEdgeDetectionImageFilter}
//
//  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::ZeroCrossingBasedEdgeDetectionImageFilter!header}
//
//  Software Guide : EndLatex
 
// Software Guide : BeginCodeSnippet
#include "itkZeroCrossingBasedEdgeDetectionImageFilter.h"
// Software Guide : EndCodeSnippet
 
#include "itkRescaleIntensityImageFilter.h"
 
 
int
main(int argc, char * argv[])
{
  if (argc < 5)
  {
    std::cerr << "Usage: " << std::endl;
    std::cerr << argv[0]
              << "  inputImageFile   outputImageFile variance maxerror"
              << std::endl;
    return EXIT_FAILURE;
  }
 
  // Software Guide : BeginCodeSnippet
  using InputPixelType = double;
  using OutputPixelType = double;
  using CharPixelType = unsigned char;
 
  constexpr unsigned int Dimension = 2;
 
  using InputImageType = itk::Image<InputPixelType, Dimension>;
  using OutputImageType = itk::Image<OutputPixelType, Dimension>;
  using CharImageType = itk::Image<CharPixelType, Dimension>;
  // Software Guide : EndCodeSnippet
 
  using ReaderType = itk::ImageFileReader<InputImageType>;
  using WriterType = itk::ImageFileWriter<CharImageType>;
 
  using RescaleFilterType =
    itk::RescaleIntensityImageFilter<OutputImageType, CharImageType>;
 
  auto reader = ReaderType::New();
  auto writer = WriterType::New();
 
  auto rescaler = RescaleFilterType::New();
 
  reader->SetFileName(argv[1]);
  writer->SetFileName(argv[2]);
 
  using FilterType =
    itk::ZeroCrossingBasedEdgeDetectionImageFilter<InputImageType,
                                                   OutputImageType>;
  auto filter = FilterType::New();
 
 
  //  Software Guide : BeginLatex
  //
  //  The filter requires two parameters. First the value of the variance to
  //  be used by the Gaussian smoothing stage. This value is provided in the
  //  method \code{SetVariance} and it is given in pixel units. Second the
  //  filter expects the acceptable error for computing the approximation to
  //  the Gaussian kernel. This error is expected to be in the range between 0
  //  and 1. Values outside that range will result in Exceptions being thrown.
  //
  //
  //  \index{itk::ZeroCrossingBasedEdgeDetectionImageFilter!SetVariance}
  //  \index{itk::ZeroCrossingBasedEdgeDetectionImageFilter!SetMaximumError}
  //
  //  Software Guide : EndLatex
 
  // Software Guide : BeginCodeSnippet
  filter->SetVariance(std::stod(argv[3]));
  filter->SetMaximumError(std::stod(argv[4]));
  // Software Guide : EndCodeSnippet
 
 
  //  Software Guide : BeginLatex
  //
  //  As with most filters, we connect the input and output of this
  //  filter in order to create a pipeline. In this particular case the
  //  input is taken from a reader and the output is sent to a writer.
  //  Given that the zero crossing filter is producing a float image as
  //  output, we use a \doxygen{RescaleIntensityImageFilter} to convert
  //  this image to an eight bits image before sending it to the writer.
  //
  //  Software Guide : EndLatex
 
  // Software Guide : BeginCodeSnippet
  filter->SetInput(reader->GetOutput());
  rescaler->SetInput(filter->GetOutput());
  writer->SetInput(rescaler->GetOutput());
  // Software Guide : EndCodeSnippet
 
  rescaler->SetOutputMinimum(0);
  rescaler->SetOutputMaximum(255);
 
  try
  {
    writer->Update();
  }
  catch (const itk::ExceptionObject & excp)
  {
    std::cerr << excp << std::endl;
  }
 
 
  return EXIT_SUCCESS;
}