otbNeighborhoodMajorityVotingImageFilter.hxx

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/*
 * Copyright (C) 2005-2022 Centre National d'Etudes Spatiales (CNES)
 *
 * This file is part of Orfeo Toolbox
 *
 *     https://www.orfeo-toolbox.org/
 *
 * 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
 *
 * 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.
 */
 
#ifndef otbNeighborhoodMajorityVotingImageFilter_hxx
#define otbNeighborhoodMajorityVotingImageFilter_hxx
 
// First make sure that the configuration is available.
// This line can be removed once the optimized versions
// gets integrated into the main directories.
 
#include "otbNeighborhoodMajorityVotingImageFilter.h"
#include "itkDefaultConvertPixelTraits.h"
#include "itkMetaDataObject.h"
#include "otbMetaDataKey.h"
#include "otbNoDataHelper.h"
 
namespace otb
{
template <class TInputImage, class TOutputImage, class TKernel>
NeighborhoodMajorityVotingImageFilter<TInputImage, TOutputImage, TKernel>::NeighborhoodMajorityVotingImageFilter()
{
  this->SetLabelForNoDataPixels(itk::NumericTraits<PixelType>::NonpositiveMin());    // m_LabelForNoDataPixels = 0
  this->SetLabelForUndecidedPixels(itk::NumericTraits<PixelType>::NonpositiveMin()); // m_LabelForUndecidedPixels = 0
  this->SetKeepOriginalLabelBool(true);                                              // m_KeepOriginalLabelBool = true
  this->SetOnlyIsolatedPixels(false);                                                // process all pixels
  this->SetIsolatedThreshold(1);
}
 
 
template <class TInputImage, class TOutputImage, class TKernel>
typename NeighborhoodMajorityVotingImageFilter<TInputImage, TOutputImage, TKernel>::PixelType
NeighborhoodMajorityVotingImageFilter<TInputImage, TOutputImage, TKernel>::Evaluate(const NeighborhoodIteratorType& nit, const KernelIteratorType kernelBegin,
                                                                                    const KernelIteratorType kernelEnd)
{
  const PixelType centerPixel = nit.GetCenterPixel();
  if (centerPixel == m_LabelForNoDataPixels)
  {
    return m_LabelForNoDataPixels;
  }
  else
  {
    // Get a histogram of label frequencies where the 2 highest are at the beginning and sorted
    const HistoSummary histoSummary = this->ComputeNeighborhoodHistogramSummary(nit, kernelBegin, kernelEnd);
    if (m_OnlyIsolatedPixels && histoSummary.freqCenterLabel > m_IsolatedThreshold)
    {
      // If we want to filter only isolated pixels, keep the label if
      // there are enough pixels with the center label to consider that
      // it is not isolated
      return centerPixel;
    }
    else
    {
      // If the majorityLabel is NOT unique in the neighborhood
      if (!histoSummary.majorityUnique)
      {
        if (m_KeepOriginalLabelBool == true)
        {
          return centerPixel;
        }
        else
        {
          return m_LabelForUndecidedPixels;
        }
      }
      // Extraction of the more representative Label in the neighborhood (majorityLabel)
      return histoSummary.majorityLabel;
    }
  } // END if (centerPixel != m_LabelForNoDataPixels)
}
 
template <class TInputImage, class TOutputImage, class TKernel>
const typename NeighborhoodMajorityVotingImageFilter<TInputImage, TOutputImage, TKernel>::HistoSummary
NeighborhoodMajorityVotingImageFilter<TInputImage, TOutputImage, TKernel>::ComputeNeighborhoodHistogramSummary(const NeighborhoodIteratorType& nit,
                                                                                                               const KernelIteratorType kernelBegin,
                                                                                                               const KernelIteratorType kernelEnd) const
{
  typedef std::map<PixelType, unsigned int>               HistogramType;
  typedef std::vector<std::pair<PixelType, unsigned int>> HistoAsVectorType;
  HistogramType histoNeigh;
  unsigned int  i = 0;
  for (KernelIteratorType kernel_it = kernelBegin; kernel_it < kernelEnd; ++kernel_it, ++i)
  {
    // if structuring element is positive, use the pixel under that element
    // in the image
    // note we use GetPixel() on the SmartNeighborhoodIterator to
    // respect boundary conditions
    const PixelType label = nit.GetPixel(i);
    if ((*kernel_it > itk::NumericTraits<KernelPixelType>::Zero) && (label != m_LabelForNoDataPixels))
    {
      histoNeigh[label] += 1;
    }
  }
  typename NeighborhoodMajorityVotingImageFilter<TInputImage, TOutputImage, TKernel>::HistoSummary result;
  assert(!histoNeigh.empty());
  if (histoNeigh.size() == 1)
  {
    result.freqCenterLabel = histoNeigh.begin()->second;
    result.majorityLabel   = histoNeigh.begin()->first;
    result.majorityUnique  = true;
  }
  else
  {
    HistoAsVectorType histoNeighVec(histoNeigh.begin(), histoNeigh.end());
    // Sort the 2 max elements to the beginning
    std::nth_element(histoNeighVec.begin(), histoNeighVec.begin() + 1, histoNeighVec.end(), CompareHistoFequencies());
    result.freqCenterLabel = histoNeigh[nit.GetCenterPixel()];
    result.majorityLabel   = histoNeighVec[0].first;
    result.majorityUnique  = (histoNeighVec[0].second != histoNeighVec[1].second);
  }
  return result;
}
 
template <class TInputImage, class TOutputImage, class TKernel>
void NeighborhoodMajorityVotingImageFilter<TInputImage, TOutputImage, TKernel>::GenerateOutputInformation()
{
  Superclass::GenerateOutputInformation();
 
  TOutputImage* outputPtr = this->GetOutput();
 
  // Set the NoData value using the background
  const unsigned int& nbBands = outputPtr->GetNumberOfComponentsPerPixel();
  std::vector<bool>   noDataValueAvailable;
  noDataValueAvailable.resize(nbBands, true);
  std::vector<double> noDataValue;
  noDataValue.resize(nbBands, 0.0);
  for (unsigned int i = 0; i < nbBands; ++i)
  {
    noDataValue[i] = itk::DefaultConvertPixelTraits<PixelType>::GetNthComponent(i, m_LabelForNoDataPixels);
  }
 
  WriteNoDataFlags(noDataValueAvailable, noDataValue, outputPtr->GetImageMetadata());
}
 
} // end namespace otb
 
#endif