itkStandardDeviationProjectionImageFilter.h

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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 __itkStandardDeviationProjectionImageFilter_h
#define __itkStandardDeviationProjectionImageFilter_h

#include "itkProjectionImageFilter.h"
#include "itkConceptChecking.h"

namespace itk
{
namespace Functor
{
template< typename TInputPixel, typename TAccumulate >
class StandardDeviationAccumulator
{
public:
  typedef typename NumericTraits< TInputPixel >::RealType RealType;

  StandardDeviationAccumulator( SizeValueType size )
  {
    m_Size = size;
    m_Values.reserve(size);
  }

  ~StandardDeviationAccumulator(){}

  inline void Initialize()
  {
    m_Sum = NumericTraits< TAccumulate >::Zero;
    m_Values.clear();
  }

  inline void operator()(const TInputPixel & input)
  {
    m_Sum = m_Sum + input;
    m_Values.push_back(input);
  }

  inline RealType GetValue()
  {
    // to avoid division by zero
    if ( m_Size <= 1 )
      {
      return NumericTraits< RealType >::Zero;
      }

    typename NumericTraits< TInputPixel >::RealType mean =
      ( (RealType)m_Sum ) / m_Size;
    typename std::vector< TInputPixel >::iterator it;
    RealType squaredSum = NumericTraits< RealType >::Zero;
    for ( it = m_Values.begin(); it != m_Values.end(); it++ )
      {
      squaredSum += vnl_math_sqr(*it - mean);
      }
    return std::sqrt( squaredSum / ( m_Size - 1 ) );
  }

  TAccumulate                m_Sum;
  SizeValueType              m_Size;
  std::vector< TInputPixel > m_Values;
};
} // end namespace Function

template< typename TInputImage,
          typename TOutputImage,
          typename TAccumulate = typename
                              NumericTraits< typename TOutputImage::PixelType >
                              ::AccumulateType >
class StandardDeviationProjectionImageFilter:
  public
  ProjectionImageFilter< TInputImage, TOutputImage,
                         Functor::StandardDeviationAccumulator< typename
                                                                TInputImage::PixelType, TAccumulate > >
{
public:
  typedef StandardDeviationProjectionImageFilter Self;

  typedef ProjectionImageFilter< TInputImage, TOutputImage,
                                 Functor::StandardDeviationAccumulator< typename
                                                                        TInputImage::PixelType,
                                                                        TAccumulate > > Superclass;

  typedef TInputImage                        InputImageType;
  typedef typename InputImageType::PixelType InputPixelType;

  typedef SmartPointer< Self >       Pointer;
  typedef SmartPointer< const Self > ConstPointer;

  itkTypeMacro(StandardDeviationProjectionImageFilter, ProjectionImageFilter);

  itkNewMacro(Self);

#ifdef ITK_USE_CONCEPT_CHECKING
  // Begin concept checking
  itkConceptMacro( InputPixelToOutputPixelTypeGreaterAdditiveOperatorCheck,
                   ( Concept::AdditiveOperators< TAccumulate,
                                                 InputPixelType,
                                                 TAccumulate > ) );
  itkConceptMacro( InputHasNumericTraitsCheck,
                   ( Concept::HasNumericTraits< InputPixelType > ) );

  itkConceptMacro( AccumulateHasNumericTraitsCheck,
                   ( Concept::HasNumericTraits< TAccumulate > ) );

  // End concept checking
#endif

protected:
  StandardDeviationProjectionImageFilter() {}
  virtual ~StandardDeviationProjectionImageFilter() {}

private:
  //purposely not implemented
  StandardDeviationProjectionImageFilter(const Self &);

  void operator=(const Self &); //purposely not implemented
};                              // end StandardDeviationProjectionImageFilter
} //end namespace itk

#endif