/usr/include/ITK-4.5/itkCompositeValleyFunction.h is in libinsighttoolkit4-dev 4.5.0-3.
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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 __itkCompositeValleyFunction_h
#define __itkCompositeValleyFunction_h
#include "itkCacheableScalarFunction.h"
#include <vector>
namespace itk
{
/** \class CompositeValleyFunction
* \brief Multiple valley shaped curve function
*
* Its functional form f(x) is :
* sum (valley( (x - mean[i]) / sigma[i] ) )
* over i from 0 to the number of target classes
* where valley(x) = 1 - 1 / (1 + x^2 / 3)
*
* The plotting of the function return shows multiple lowest points at each
* mean[i] position. There are two more important shape parameters for this
* function, higher-bound and lower-bound. Upper-bound will be highest mean
* value among target classes' means + its sigma value * 9, and lower-bound
* will be lowest mean value among target classes' means - its sigma value * 9
*
* For example, if there are two target classes with their means at 4 and 6.
* The plotting may look like the following:
*
* |
* |********* ******
* | * *
* | * * *
* | * * * *
* | * * * *
* | * * * *
* | * *
* ---+-----+------*------*-------
* | 2 4 6
* |
*
*
* This is a part of the bias correction methods and implementaion that
* was initially developed and implemented
* by Martin Styner, Univ. of North Carolina at Chapel Hill, and his
* colleagues.
*
* For more details. refer to the following articles.
* "Parametric estimate of intensity inhomogeneities applied to MRI"
* Martin Styner, G. Gerig, Christian Brechbuehler, Gabor Szekely,
* IEEE TRANSACTIONS ON MEDICAL IMAGING; 19(3), pp. 153-165, 2000,
* (http://www.cs.unc.edu/~styner/docs/tmi00.pdf)
*
* "Evaluation of 2D/3D bias correction with 1+1ES-optimization"
* Martin Styner, Prof. Dr. G. Gerig (IKT, BIWI, ETH Zuerich), TR-197
* (http://www.cs.unc.edu/~styner/docs/StynerTR97.pdf)
* \ingroup ITKBiasCorrection
*/
class TargetClass
{
public:
/** Constructor. */
TargetClass(double mean, double sigma)
{
m_Mean = mean;
m_Sigma = sigma;
}
/** Set/Get the mean of the function. */
void SetMean(double mean) { m_Mean = mean; }
double GetMean() { return m_Mean; }
/** Set/Get the standard deviation of the function. */
void SetSigma(double sigma) { m_Sigma = sigma; }
double GetSigma() { return m_Sigma; }
private:
double m_Mean;
double m_Sigma;
}; // end of class
class CompositeValleyFunction:public CacheableScalarFunction
{
public:
/** Superclass to this class. */
typedef CacheableScalarFunction Superclass;
/** Cost value type. */
typedef Superclass::MeasureType MeasureType;
typedef Superclass::MeasureArrayType MeasureArrayType;
/** Constructor. */
CompositeValleyFunction(const MeasureArrayType & classMeans,
const MeasureArrayType & classSigmas);
/** Destructor. */
virtual ~CompositeValleyFunction() {}
/** Get energy table's higher bound. */
double GetUpperBound() { return m_UpperBound; }
/** Get energy table's lower bound. */
double GetLowerBound() { return m_LowerBound; }
/** Gets an energy value for the intensity difference between a pixel
* and its corresponding bias. */
MeasureType operator()(MeasureType x)
{
if ( x > m_UpperBound || x < m_LowerBound )
{
return 1;
}
if ( !this->IsCacheAvailable() )
{
return this->Evaluate(x);
}
else
{
return GetCachedValue(x);
}
}
/** Evalaute the function at point x. */
inline MeasureType Evaluate(MeasureType x)
{
MeasureType res = 1;
for ( unsigned int k = 0; k < m_Targets.size(); k++ )
{
res *= valley( ( x - m_Targets[k].GetMean() )
/ m_Targets[k].GetSigma() );
}
return res;
}
/** Get an energy value for the valley. */
inline MeasureType valley(MeasureType d)
{
return 1 - 1 / ( 1 + d * d / 3 );
}
protected:
void AddNewClass(double mean, double sigma)
{
TargetClass aClass(mean, sigma);
m_Targets.push_back(aClass);
}
/** calculate and save energy values */
void Initialize();
private:
/** Storage for tissue classes' statistics. */
std::vector< TargetClass > m_Targets;
/** The highest mean value + the sigma of the tissue class
* which has the highest mean value * 9. */
double m_UpperBound;
/** The lowest mean value - the sigma of the tissue class
* which has the lowest mean value * 9. */
double m_LowerBound;
}; // end of class
} // end of namespace itk
#endif
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