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/*=========================================================================
Program: Insight Segmentation & Registration Toolkit
Module: $RCSfile: itkHistogramToLogProbabilityImageFilter.h,v $
Language: C++
Date: $Date: 2009-04-06 11:51:06 $
Version: $Revision: 1.11 $
Copyright (c) Insight Software Consortium. All rights reserved.
See ITKCopyright.txt or http://www.itk.org/HTML/Copyright.htm for details.
This software is distributed WITHOUT ANY WARRANTY; without even
the implied warranty of MERCHANTABILITY or FITNESS FOR A PARTICULAR
PURPOSE. See the above copyright notices for more information.
=========================================================================*/
#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
*
*/
namespace Function {
template< class TInput, class TOutput=double >
class HistogramLogProbabilityFunction
{
public:
//Probability function = Number of occurances in each bin /
// Total Number of occurances.
//
// 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>(vcl_log( static_cast<OutputPixelType>(A) /
static_cast<OutputPixelType>(m_TotalFrequency)) / vcl_log(2.0) );
}
else
{ // Check for Log 0. Always assume that the frequency is atleast 1.
return static_cast<OutputPixelType>(vcl_log( static_cast<OutputPixelType>(A+1) /
static_cast<OutputPixelType>(m_TotalFrequency)) / vcl_log(2.0) );
}
}
void SetTotalFrequency( unsigned long n )
{
m_TotalFrequency = n;
}
unsigned long GetTotalFrequency( ) const
{
return m_TotalFrequency;
}
private:
unsigned long m_TotalFrequency;
};
}
template <class THistogram, class TOutputPixel=double >
class ITK_EXPORT HistogramToLogProbabilityImageFilter :
public HistogramToImageFilter< THistogram,
Function::HistogramLogProbabilityFunction< unsigned long, TOutputPixel > >
{
public:
/** Standard class typedefs. */
typedef HistogramToLogProbabilityImageFilter Self;
/** Standard "Superclass" typedef. */
typedef HistogramToImageFilter< THistogram,
Function::HistogramLogProbabilityFunction< unsigned long, TOutputPixel > >
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() {}
private:
HistogramToLogProbabilityImageFilter(const Self&); //purposely not implemented
void operator=(const Self&); //purposely not implemented
};
} // end namespace itk
#endif
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