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/*========================================================================= |
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Program: Insight Segmentation & Registration Toolkit |
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Module: $RCSfile: itkBSplineKernelFunction.h.html,v $ |
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Language: C++ |
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Date: $Date: 2006/01/17 19:15:33 $ |
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Version: $Revision: 1.4 $ |
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Copyright (c) Insight Software Consortium. All rights reserved. |
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See ITKCopyright.txt or http://www.itk.org/HTML/Copyright.htm for details. |
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This software is distributed WITHOUT ANY WARRANTY; without even |
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the implied warranty of MERCHANTABILITY or FITNESS FOR A PARTICULAR |
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PURPOSE. See the above copyright notices for more information. |
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=========================================================================*/ |
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DEF |
#ifndef _itkBSplineKernelFunction_h |
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DEF |
#define _itkBSplineKernelFunction_h |
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#include "itkKernelFunction.h" |
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#include "vnl/vnl_math.h" |
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namespace itk |
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{ |
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/** \class BSplineKernelFunction |
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* \brief BSpline kernel used for density estimation and nonparameteric |
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* regression. |
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* |
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* This class enscapsulates BSpline kernel for |
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* density estimation or nonparameteric regression. |
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* See documentation for KernelFunction for more details. |
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* |
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* This class is templated over the spline order. |
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* \warning Evaluate is only implemented for spline order 0 to 3 |
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* |
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* \sa KernelFunction |
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* |
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* \ingroup Functions |
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*/ |
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template <unsigned int VSplineOrder = 3> |
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class ITK_EXPORT BSplineKernelFunction : public KernelFunction |
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{ |
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public: |
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/** Standard class typedefs. */ |
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typedef BSplineKernelFunction Self; |
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TDA |
typedef KernelFunction Superclass; |
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TDA |
typedef SmartPointer<Self> Pointer; |
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/** Method for creation through the object factory. */ |
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itkNewMacro(Self); |
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/** Run-time type information (and related methods). */ |
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itkTypeMacro(BSplineKernelFunction, KernelFunction); |
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/** Enum of for spline order. */ |
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itkStaticConstMacro(SplineOrder, unsigned int, VSplineOrder); |
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/** Evaluate the function. */ |
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inline double Evaluate( const double & u ) const |
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{ |
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return this->Evaluate( Dispatch<VSplineOrder>(), u ); |
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} |
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protected: |
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BSplineKernelFunction(){}; |
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~BSplineKernelFunction(){}; |
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void PrintSelf(std::ostream& os, Indent indent) const |
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{ |
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Superclass::PrintSelf( os, indent ); |
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os << indent << "Spline Order: " << SplineOrder << std::endl; |
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} |
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private: |
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BSplineKernelFunction(const Self&); //purposely not implemented |
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void operator=(const Self&); //purposely not implemented |
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/** Structures to control overloaded versions of Evaluate */ |
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struct DispatchBase {}; |
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template<unsigned int> |
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struct Dispatch : DispatchBase {}; |
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/** Zeroth order spline. */ |
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inline double Evaluate (const Dispatch<0>&, const double & u) const |
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{ |
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double absValue = vnl_math_abs( u ); |
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if ( absValue < 0.5 ) |
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{ |
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return 1.0; |
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} |
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else if ( absValue == 0.5 ) |
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{ |
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return 0.5; |
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} |
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else |
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{ |
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return 0.0; |
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} |
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} |
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/** First order spline */ |
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inline double Evaluate ( const Dispatch<1>&, const double& u) const |
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{ |
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double absValue = vnl_math_abs( u ); |
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if ( absValue < 1.0 ) |
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{ |
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return 1.0 - absValue; |
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} |
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else |
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{ |
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return 0.0; |
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} |
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} |
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/** Second order spline. */ |
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inline double Evaluate ( const Dispatch<2>&, const double& u) const |
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{ |
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double absValue = vnl_math_abs( u ); |
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if ( absValue < 0.5 ) |
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{ |
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return 0.75 - vnl_math_sqr( absValue ); |
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} |
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else if ( absValue < 1.5 ) |
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{ |
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return ( 9.0 - 12.0 * absValue + 4.0 * vnl_math_sqr( absValue ) ) / 8.0; |
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} |
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else |
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{ |
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return 0.0; |
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} |
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} |
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/** Third order spline. */ |
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inline double Evaluate ( const Dispatch<3>&, const double& u) const |
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{ |
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double absValue = vnl_math_abs( u ); |
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double sqrValue = vnl_math_sqr( u ); |
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if ( absValue < 1.0 ) |
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{ |
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return ( 4.0 - 6.0 * sqrValue + 3.0 * sqrValue * absValue ) / 6.0; |
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} |
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else if ( absValue < 2.0 ) |
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{ |
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return ( 8.0 - 12 * absValue + 6.0 * sqrValue - sqrValue * absValue ) / 6.0; |
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} |
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else |
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{ |
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return 0.0; |
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} |
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} |
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/** Unimplemented spline order */ |
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inline double Evaluate ( const DispatchBase&, const double&) const |
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{ |
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itkExceptionMacro("Evaluate not implemented for spline order " << SplineOrder); |
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return 0.0; //This is to avoid compiler warning about missing return statement. It should never be evaluated. |
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} |
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}; |
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EML |
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} // namespace itk |
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#endif |
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