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

  Program:   Insight Segmentation & Registration Toolkit
  Module:    $RCSfile: itkMutualInformationHistogramImageToImageMetric.h,v $
  Language:  C++
  Date:      $Date: 2003/09/10 14:28:35 $
  Version:   $Revision: 1.3 $

  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 __itkMutualInformationHistogramImageToImageMetric_h
#define __itkMutualInformationHistogramImageToImageMetric_h

#include "itkHistogramImageToImageMetric.h"

namespace itk
{
  /** \class MutualInformationHistogramImageToImageMetric
      \brief Computes the mutual information between two images to
      be registered using the histograms of the intensities in the images.

      This class is templated over the type of the fixed and moving
      images to be compared.

      This metric computes the similarity measure between pixels in the
      moving image and pixels in the fixed images using a histogram.

      \ingroup RegistrationMetrics */
template <class TFixedImage, class TMovingImage>
class ITK_EXPORT MutualInformationHistogramImageToImageMetric :
public HistogramImageToImageMetric<TFixedImage, TMovingImage>
{
 public:
  /** Standard class typedefs. */
  typedef MutualInformationHistogramImageToImageMetric Self;
  typedef HistogramImageToImageMetric<TFixedImage, TMovingImage> Superclass;
  typedef SmartPointer<Self>                                     Pointer;
  typedef SmartPointer<const Self>                               ConstPointer;

  /** Method for creation through the object factory. */
  itkNewMacro(Self);

  /** Run-time type information (and related methods). */
  itkTypeMacro(MutualInformationHistogramImageToImageMetric,
    HistogramImageToImageMetric);

  /** Types transferred from the base class */
  typedef typename Superclass::RealType                 RealType;
  typedef typename Superclass::TransformType            TransformType;
  typedef typename Superclass::TransformPointer         TransformPointer;
  typedef typename Superclass::TransformParametersType
    TransformParametersType;
  typedef typename Superclass::TransformJacobianType    TransformJacobianType;
  typedef typename Superclass::GradientPixelType        GradientPixelType;

  typedef typename Superclass::MeasureType              MeasureType;
  typedef typename Superclass::DerivativeType           DerivativeType;
  typedef typename Superclass::FixedImageType           FixedImageType;
  typedef typename Superclass::MovingImageType          MovingImageType;
  typedef typename Superclass::FixedImageConstPointer   FixedImageConstPointer;
  typedef typename Superclass::MovingImageConstPointer
    MovingImageConstPointer;

  typedef typename Superclass::HistogramType            HistogramType;
  typedef typename HistogramType::FrequencyType         HistogramFrequencyType;
  typedef typename HistogramType::Iterator              HistogramIteratorType;
  typedef typename HistogramType::MeasurementVectorType
    HistogramMeasurementVectorType;

protected:
  /** Constructor is protected to ensure that \c New() function is used to
      create instances. */
  MutualInformationHistogramImageToImageMetric(){}
  virtual ~MutualInformationHistogramImageToImageMetric(){}

  /** Evaluates the mutual information from the histogram. */
  virtual MeasureType EvaluateMeasure(HistogramType& histogram) const;

private:
  // Purposely not implemented.
  MutualInformationHistogramImageToImageMetric(Self const&);
  void operator=(Self const&); // Purposely not implemented.
};

} // End namespace itk.

#ifndef ITK_MANUAL_INSTANTIATION
#include "itkMutualInformationHistogramImageToImageMetric.txx"
#endif

#endif // __itkMutualInformationHistogramImageToImageMetric_h
