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/*
* Copyright (C) 2005-2020 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 otbJoinHistogramMI_h
#define otbJoinHistogramMI_h
#include "itkHistogram.h"
namespace otb
{
namespace Functor
{
template <class TInput1, class TInput2, class TOutput>
class JoinHistogramMI
{
public:
typedef double HistogramFrequencyType;
typedef typename itk::Statistics::Histogram<HistogramFrequencyType, itk::Statistics::DenseFrequencyContainer2> HistogramType;
JoinHistogramMI()
{
}
virtual ~JoinHistogramMI()
{
}
inline TOutput operator()(const TInput1& itA, const TInput2& itB, const HistogramType* histogram)
{
TOutput jointEntropy = itk::NumericTraits<TOutput>::Zero;
HistogramFrequencyType totalFreq = histogram->GetTotalFrequency();
typename HistogramType::MeasurementVectorType sample(2);
for (unsigned long pos = 0; pos < itA.Size(); ++pos)
{
double valueA = static_cast<double>(itA.GetPixel(pos));
double valueB = static_cast<double>(itB.GetPixel(pos));
sample[0] = valueA;
sample[1] = valueB;
typename HistogramType::IndexType index;
histogram->GetIndex(sample, index);
HistogramFrequencyType freq = histogram->GetFrequency(index);
if (freq > 0)
{
jointEntropy += freq * std::log(freq);
}
}
jointEntropy = -jointEntropy / static_cast<TOutput>(totalFreq) + std::log(totalFreq);
return jointEntropy;
}
};
}
} // end namespace otb
#endif
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