freDifferenceEnergyImageToImageMetric.txx

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/*=========================================================================

  Program:   F.R.E.E. - flexible registration evaluation engine
  Version:   v.1.0.0
  Date:      $Date: 2006/09/01 12:00:00 $
  Module:    $RCSfile: freDifferenceEnergyImageToImageMetric.txx,v $
  Language:  C++



  Copyright (c) 2007 Ralf o Floca (Department of Medical Informatics,
  Institute for Medical Biometry and Informatics, University of Heidelberg,
  Germany). All rights reserved.
  See FREECopyright.txt or http://www.mi.med.uni-hd.de/free/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 __freDifferenceEnergyImageToImageMetric_txx
#define __freDifferenceEnergyImageToImageMetric_txx

#include "freDifferenceEnergyImageToImageMetric.h"

namespace itk
{
template <class TFixedImage, class TMovingImage, class TDifImage>
  typename DifferenceEnergyImageToImageMetric<TFixedImage, TMovingImage, TDifImage>
  ::MeasureType
  DifferenceEnergyImageToImageMetric<TFixedImage, TMovingImage, TDifImage>
  ::EvaluateMeasure(HistogramType& histogram) const
  {
    MeasureType measure = NumericTraits<MeasureType>::Zero;
    HistogramIteratorType it = histogram.Begin();
    HistogramIteratorType end = histogram.End();
    HistogramFrequencyType totalFrequency = histogram.GetTotalFrequency();

    while (it != end)
      {
      HistogramFrequencyType freq = it.GetFrequency();
      if (freq > 0)
        {
        MeasureType energy = freq/totalFrequency;
                                energy *= energy;
                                measure += energy;
        }
      ++it;
      }

                //negate the measure because some optimizers (e.g. can only minimize)
    return -1*measure;
  }
} // End namespace itk


#endif // __freDifferenceEnergyImageToImageMetric_txx

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