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itkMutualInformationHistogramImageToImageMetric.hxx
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itkMutualInformationHistogramImageToImageMetric.hxx
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/*=========================================================================
*
* 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.
*
*=========================================================================*/
#ifndef itkMutualInformationHistogramImageToImageMetric_hxx
#define itkMutualInformationHistogramImageToImageMetric_hxx
#include "itkMutualInformationHistogramImageToImageMetric.h"
#include "itkHistogram.h"
namespace itk
{
template< typename TFixedImage, typename TMovingImage >
typename MutualInformationHistogramImageToImageMetric< TFixedImage, TMovingImage >::MeasureType
MutualInformationHistogramImageToImageMetric< TFixedImage, TMovingImage >
::EvaluateMeasure(HistogramType & histogram) const
{
MeasureType entropyX = NumericTraits< MeasureType >::ZeroValue();
MeasureType entropyY = NumericTraits< MeasureType >::ZeroValue();
MeasureType jointEntropy = NumericTraits< MeasureType >::ZeroValue();
typedef typename NumericTraits< HistogramFrequencyType >::RealType HistogramFrequencyRealType;
HistogramFrequencyRealType totalFreq =
static_cast< HistogramFrequencyRealType >( histogram.GetTotalFrequency() );
for ( unsigned int i = 0; i < this->GetHistogramSize()[0]; i++ )
{
HistogramFrequencyRealType freq =
static_cast< HistogramFrequencyRealType >( histogram.GetFrequency(i, 0) );
if ( freq > 0 )
{
entropyX += freq * std::log(freq);
}
}
entropyX = -entropyX / static_cast< MeasureType >( totalFreq ) + std::log(totalFreq);
for ( unsigned int i = 0; i < this->GetHistogramSize()[1]; i++ )
{
HistogramFrequencyRealType freq =
static_cast< HistogramFrequencyRealType >( histogram.GetFrequency(i, 1) );
if ( freq > 0 )
{
entropyY += freq * std::log(freq);
}
}
entropyY = -entropyY / static_cast< MeasureType >( totalFreq ) + std::log(totalFreq);
HistogramIteratorType it = histogram.Begin();
HistogramIteratorType end = histogram.End();
while ( it != end )
{
HistogramFrequencyRealType freq =
static_cast< HistogramFrequencyRealType >( it.GetFrequency() );
if ( freq > 0 )
{
jointEntropy += freq * std::log(freq);
}
++it;
}
jointEntropy = -jointEntropy
/ static_cast< MeasureType >( totalFreq ) + std::log(totalFreq);
return entropyX + entropyY - jointEntropy;
}
} // End namespace itk
#endif // itkMutualInformationHistogramImageToImageMetric_hxx