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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 itkHistogramToLogProbabilityImageFilter_h
#define itkHistogramToLogProbabilityImageFilter_h
#include "itkHistogramToImageFilter.h"
namespace itk
{
/** \class HistogramToLogProbabilityImageFilter
* \brief The class takes a histogram as an input and gives the log probability
* image as the output. A pixel, at position I, in the output image is given by
*
* \f[
* f(I) = \log_2( \frac{q_I}{\sum_{i \in I} q_I} )
* \f]
* where \f$q_I\f$ is the frequency of measurement vector, I.
*
* This is the log of the frequency of a measurement vector by the sum of all
* frequencies.
*
* The output image is of type double.
*
* This is useful in plotting the joint histograms during registration.
*
* \sa HistogramToImageFilter, HistogramToProbabilityImageFilter,
* HistogramToIntensityImageFilter, HistogramToEntropyImageFilter
*
* \ingroup ITKStatistics
*/
namespace Function
{
template< typename TInput, typename TOutput = double >
class HistogramLogProbabilityFunction
{
public:
//Probability function = Number of occurrences in each bin /
// Total Number of occurrences.
//
// Returns pixels of float..
typedef TOutput OutputPixelType;
HistogramLogProbabilityFunction():
m_TotalFrequency(1) {}
~HistogramLogProbabilityFunction() {}
inline OutputPixelType operator()(const TInput & A) const
{
if ( A )
{
return static_cast< OutputPixelType >( std::log( static_cast< OutputPixelType >( A )
/ static_cast< OutputPixelType >( m_TotalFrequency ) )
/ std::log(2.0) );
}
else
{ // Check for Log 0. Always assume that the frequency is atleast 1.
return static_cast< OutputPixelType >( std::log( static_cast< OutputPixelType >( A + 1 )
/ static_cast< OutputPixelType >( m_TotalFrequency ) )
/ std::log(2.0) );
}
}
void SetTotalFrequency(SizeValueType n)
{
m_TotalFrequency = n;
}
SizeValueType GetTotalFrequency() const
{
return m_TotalFrequency;
}
private:
SizeValueType m_TotalFrequency;
};
}
template< typename THistogram, typename TImage=Image< double, 3 > >
class HistogramToLogProbabilityImageFilter:
public HistogramToImageFilter< THistogram, TImage,
Function::HistogramLogProbabilityFunction< SizeValueType, typename TImage::PixelType > >
{
public:
/** Standard class typedefs. */
typedef HistogramToLogProbabilityImageFilter Self;
/** Standard "Superclass" typedef. */
typedef HistogramToImageFilter< THistogram, TImage,
Function::HistogramLogProbabilityFunction< SizeValueType, typename TImage::PixelType > >
Superclass;
typedef SmartPointer< Self > Pointer;
typedef SmartPointer< const Self > ConstPointer;
/** Run-time type information (and related methods). */
itkTypeMacro(HistogramToLogProbabilityImageFilter, HistogramToImageFilter);
/** Method for creation through the object factory. */
itkNewMacro(Self);
protected:
HistogramToLogProbabilityImageFilter() {}
virtual ~HistogramToLogProbabilityImageFilter() ITK_OVERRIDE {}
private:
ITK_DISALLOW_COPY_AND_ASSIGN(HistogramToLogProbabilityImageFilter);
};
} // end namespace itk
#endif
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