SphinxExamples/src/Numerics/Statistics/ComputeHistogramFromGrayscaleImage/Code.cxx

/*=========================================================================
 *
 *  Copyright Insight Software Consortium
 *
 *  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
 *
 *         http://www.apache.org/licenses/LICENSE-2.0.txt
 *
 *  Unless required by applicable law or agreed to in writing, software
 *  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.
 *
 *=========================================================================*/

#include "itkImage.h"
#include "itkImageFileReader.h"
#include "itkImageToHistogramFilter.h"
#include "itkImageRandomIteratorWithIndex.h"

int main(int argc, char* argv[])
{
  if( argc != 3 )
    {
    std::cerr << argv[0] << "InputFileName NumberOfBins" << std::endl;
    return EXIT_FAILURE;
    }

  constexpr unsigned int Dimension = 2;
  using PixelType = unsigned char;
  using ImageType = itk::Image< PixelType, Dimension >;

  constexpr unsigned int MeasurementVectorSize = 1; // Grayscale
  const auto binsPerDimension = static_cast< unsigned int >( atoi( argv[2] ) );

  using ReaderType = itk::ImageFileReader< ImageType >;
  ReaderType::Pointer reader = ReaderType::New();
  reader->SetFileName( argv[1] );

  ImageType::Pointer image = reader->GetOutput();

  using ImageToHistogramFilterType = itk::Statistics::ImageToHistogramFilter< ImageType >;

  ImageToHistogramFilterType::HistogramType::MeasurementVectorType
    lowerBound(binsPerDimension);
  lowerBound.Fill(0);

  ImageToHistogramFilterType::HistogramType::MeasurementVectorType
    upperBound(binsPerDimension);
  upperBound.Fill(255);

  ImageToHistogramFilterType::HistogramType::SizeType
    size(MeasurementVectorSize);
  size.Fill(binsPerDimension);

  ImageToHistogramFilterType::Pointer imageToHistogramFilter =
    ImageToHistogramFilterType::New();
  imageToHistogramFilter->SetInput( image );
  imageToHistogramFilter->SetHistogramBinMinimum( lowerBound );
  imageToHistogramFilter->SetHistogramBinMaximum( upperBound );
  imageToHistogramFilter->SetHistogramSize( size );

  try
    {
    imageToHistogramFilter->Update();
    }
  catch( itk::ExceptionObject & error )
    {
    std::cerr << "Error: " << error << std::endl;
    return EXIT_FAILURE;
    }

  ImageToHistogramFilterType::HistogramType* histogram =
    imageToHistogramFilter->GetOutput();

  std::cout << "Frequency = [ ";
  for(unsigned int i = 0; i < histogram->GetSize()[0]; ++i)
    {
    std::cout << histogram->GetFrequency(i);

    if( i != histogram->GetSize()[0] - 1 )
      {
      std::cout << "," << std::endl;
      }
    }

  std::cout << " ]" << std::endl;

  return EXIT_SUCCESS;
}