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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 itkCorrelationCoefficientHistogramImageToImageMetric_hxx
#define itkCorrelationCoefficientHistogramImageToImageMetric_hxx
#include "itkCorrelationCoefficientHistogramImageToImageMetric.h"
namespace itk
{
template< typename TFixedImage, typename TMovingImage >
typename CorrelationCoefficientHistogramImageToImageMetric< TFixedImage, \
TMovingImage >::MeasureType
CorrelationCoefficientHistogramImageToImageMetric< TFixedImage, TMovingImage >
::EvaluateMeasure(HistogramType & histogram) const
{
const MeasureType varianceX = this->VarianceX(histogram);
const MeasureType varianceY = this->VarianceY(histogram);
const MeasureType covariance = this->Covariance(histogram);
return std::fabs( covariance / ( std::sqrt(varianceX) * std::sqrt(varianceY) ) );
}
template< typename TFixedImage, typename TMovingImage >
typename CorrelationCoefficientHistogramImageToImageMetric< TFixedImage, \
TMovingImage >::MeasureType
CorrelationCoefficientHistogramImageToImageMetric< TFixedImage, TMovingImage >
::MeanX(HistogramType & histogram) const
{
MeasureType meanX = NumericTraits< MeasureType >::ZeroValue();
for ( unsigned int i = 0; i < this->m_HistogramSize[0]; i++ )
{
MeasureType valX = histogram.GetMeasurement(i, 0);
HistogramFrequencyType freq = histogram.GetFrequency(i, 0);
meanX += valX * freq;
}
meanX /= histogram.GetTotalFrequency();
return meanX;
}
template< typename TFixedImage, typename TMovingImage >
typename CorrelationCoefficientHistogramImageToImageMetric< TFixedImage, \
TMovingImage >::MeasureType
CorrelationCoefficientHistogramImageToImageMetric< TFixedImage, TMovingImage >
::MeanY(HistogramType & histogram) const
{
MeasureType meanY = NumericTraits< MeasureType >::ZeroValue();
for ( unsigned int i = 0; i < this->m_HistogramSize[1]; i++ )
{
MeasureType valY = histogram.GetMeasurement(i, 1);
HistogramFrequencyType freq = histogram.GetFrequency(i, 1);
meanY += valY * freq;
}
meanY /= histogram.GetTotalFrequency();
return meanY;
}
template< typename TFixedImage, typename TMovingImage >
typename CorrelationCoefficientHistogramImageToImageMetric< TFixedImage, \
TMovingImage >::MeasureType
CorrelationCoefficientHistogramImageToImageMetric< TFixedImage, TMovingImage >
::VarianceX(HistogramType & histogram) const
{
MeasureType varX = NumericTraits< MeasureType >::ZeroValue();
for ( unsigned int i = 0; i < this->m_HistogramSize[0]; i++ )
{
varX += static_cast< double >( histogram.GetFrequency(i, 0) )
/ histogram.GetTotalFrequency()
* std::pow(histogram.GetMeasurement(i, 0), 2);
}
return varX - std::pow(MeanX(histogram), 2);
}
template< typename TFixedImage, typename TMovingImage >
typename CorrelationCoefficientHistogramImageToImageMetric< TFixedImage, \
TMovingImage >::MeasureType
CorrelationCoefficientHistogramImageToImageMetric< TFixedImage, TMovingImage >
::VarianceY(HistogramType & histogram) const
{
MeasureType varY = NumericTraits< MeasureType >::ZeroValue();
for ( unsigned int i = 0; i < this->m_HistogramSize[1]; i++ )
{
varY += static_cast< double >( histogram.GetFrequency(i, 1) )
/ histogram.GetTotalFrequency()
* std::pow(histogram.GetMeasurement(i, 1), 2);
}
return varY - std::pow(MeanY(histogram), 2);
}
template< typename TFixedImage, typename TMovingImage >
typename CorrelationCoefficientHistogramImageToImageMetric< TFixedImage, \
TMovingImage >::MeasureType
CorrelationCoefficientHistogramImageToImageMetric< TFixedImage, TMovingImage >
::Covariance(HistogramType & histogram) const
{
MeasureType var = NumericTraits< MeasureType >::ZeroValue();
MeasureType meanX = MeanX(histogram);
MeasureType meanY = MeanY(histogram);
for ( unsigned int j = 0; j < this->m_HistogramSize[1]; j++ )
{
for ( unsigned int i = 0; i < this->m_HistogramSize[0]; i++ )
{
typename HistogramType::IndexType index;
index.SetSize(2);
index[0] = i;
index[1] = j;
var += histogram.GetFrequency(index)
* ( histogram.GetMeasurement(i, 0) - meanX )
* ( histogram.GetMeasurement(j, 1) - meanY );
}
}
var /= histogram.GetTotalFrequency();
return var;
}
}
#endif // itkCorrelationCoefficientHistogramImageToImageMetric_hxx
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