text: /*=========================================================================
   *
   *  Copyright UMC Utrecht and contributors
   *
   *  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 elxMetricBase_h
  #define elxMetricBase_h
  
  /** Needed for the macros. */
  #include "elxMacro.h"
  
  #include "elxBaseComponentSE.h"
  #include "itkAdvancedImageToImageMetric.h"
  #include "itkImageGridSampler.h"
  #include "itkPointSet.h"
  
  namespace elastix
  {
  
  /**
   * \class MetricBase
   * \brief This class is the elastix base class for all  Metrics.
   *
   * This class contains the common functionality for all Metrics.
   *
   * The parameters used in this class are:
   * \parameter ShowExactMetricValue: Flag that can set to "true" or "false".
   *    If "true" the metric computes the exact metric value (computed on all
   *    voxels rather than on the set of spatial samples) and shows it each
   *    iteration. Must be given for each resolution. \n
   *    example: <tt>(ShowExactMetricValue "true" "true" "false")</tt> \n
   *    Default is "false" for all resolutions.
   * \parameter ExactMetricSampleGridSpacing: Set an integer downsampling rate for
   *    computing the "exact" metric. Only meaningful if set in combination with the
   *    ShowExactMetricValue set to "true". In some cases, it might be an overkill
   *    to really compute the exact metric with the ShowExactMetricValue.
   *    The metric computed on a downsampled image might already be accurate
   *    enough to draw conclusions about the rate of convergence for example.
   *    The downsampling rate must be given for each resolution, for each dimension.\n
   *    example: <tt>(ExactMetricSampleGridSpacing 1 1 2 2 )</tt> \n
   *    This example for a 2D registration of 2 resolutions sets the downsampling rate
   *    to 1 in the first resolution (so: use really all pixels), and to 2 in the
   *    second resolution. Default: 1 in each resolution and each dimension.
   * \parameter CheckNumberOfSamples: Whether the metric checks if at least
   *    a certain fraction (default 1/4) of the samples map inside the moving
   *    image. Can be given for each resolution or for all resolutions at once. \n
   *    example: <tt>(CheckNumberOfSamples "false" "true" "false")</tt> \n
   *    The default is true. In general it is wise to set this to true,
   *    since it detects if the registration is going really bad.
   * \parameter RequiredRatioOfValidSamples: Defines the fraction needed in
   *    CheckNumberOfSamples. \n
   *    example: <tt>(RequiredRatioOfValidSamples 0.1)</tt> \n
   *    The default is 0.25.
   *
   * \ingroup Metrics
   * \ingroup ComponentBaseClasses
   */
  
  template <class TElastix>
  class MetricBase : public BaseComponentSE<TElastix>
  {
  public:
    /** Standard ITK stuff. */
    typedef MetricBase                Self;
    typedef BaseComponentSE<TElastix> Superclass;
  
    /** Run-time type information (and related methods). */
    itkTypeMacro(MetricBase, BaseComponentSE);
  
    /** Typedef's inherited from Elastix. */
    typedef typename Superclass::ElastixType          ElastixType;
    typedef typename Superclass::ElastixPointer       ElastixPointer;
    typedef typename Superclass::ConfigurationType    ConfigurationType;
    typedef typename Superclass::ConfigurationPointer ConfigurationPointer;
    typedef typename Superclass::RegistrationType     RegistrationType;
    typedef typename Superclass::RegistrationPointer  RegistrationPointer;
  
    /** Other typedef's. */
    typedef typename ElastixType::FixedImageType  FixedImageType;
    typedef typename FixedImageType::PointType    FixedPointType;
    typedef typename FixedPointType::ValueType    FixedPointValueType;
    typedef typename ElastixType::MovingImageType MovingImageType;
    typedef typename MovingImageType::PointType   MovingPointType;
    typedef typename MovingPointType::ValueType   MovingPointValueType;
  
    /** ITKBaseType. */
    typedef itk::SingleValuedCostFunction                                    ITKBaseType;
    typedef itk::AdvancedImageToImageMetric<FixedImageType, MovingImageType> AdvancedMetricType;
    typedef typename AdvancedMetricType::MovingImageDerivativeScalesType     MovingImageDerivativeScalesType;
  
    /** Get the dimension of the fixed image. */
    itkStaticConstMacro(FixedImageDimension, unsigned int, FixedImageType::ImageDimension);
    /** Get the dimension of the moving image. */
    itkStaticConstMacro(MovingImageDimension, unsigned int, MovingImageType::ImageDimension);
  
    /** Typedefs for point sets. */
    typedef typename ITKBaseType::ParametersValueType CoordinateRepresentationType;
    typedef itk::PointSet<CoordinateRepresentationType,
                          FixedImageDimension,
                          itk::DefaultStaticMeshTraits<CoordinateRepresentationType,
                                                       FixedImageDimension,
                                                       FixedImageDimension,
                                                       CoordinateRepresentationType,
                                                       CoordinateRepresentationType,
                                                       CoordinateRepresentationType>>
      FixedPointSetType;
    typedef itk::PointSet<CoordinateRepresentationType,
                          MovingImageDimension,
                          itk::DefaultStaticMeshTraits<CoordinateRepresentationType,
                                                       MovingImageDimension,
                                                       MovingImageDimension,
                                                       CoordinateRepresentationType,
                                                       CoordinateRepresentationType,
                                                       CoordinateRepresentationType>>
      MovingPointSetType;
  
    /** Typedefs for sampler support. */
    typedef typename AdvancedMetricType::ImageSamplerType ImageSamplerBaseType;
  
    /** Return type of GetValue */
    typedef typename ITKBaseType::MeasureType MeasureType;
  
    /** Cast to ITKBaseType. */
    virtual ITKBaseType *
    GetAsITKBaseType(void)
    {
      return dynamic_cast<ITKBaseType *>(this);
    }
  
  
    /** Cast to ITKBaseType, to use in const functions. */
    virtual const ITKBaseType *
    GetAsITKBaseType(void) const
    {
      return dynamic_cast<const ITKBaseType *>(this);
    }
  
  
    /** Execute stuff before each resolution:
     * \li Check if the exact metric value should be computed
     * (to monitor the progress of the registration).
     */
    void
    BeforeEachResolutionBase(void) override;
  
    /** Execute stuff after each iteration:
     * \li Optionally compute the exact metric value and plot it to screen.
     */
    void
    AfterEachIterationBase(void) override;
  
    /** Force the metric to base its computation on a new subset of image samples.
     * Not every metric may have implemented this.
     */
    virtual void
    SelectNewSamples(void);
  
    /** Returns whether the metric uses a sampler. When the metric is not of
     * AdvancedMetricType, the function returns false immediately.
     */
    virtual bool
    GetAdvancedMetricUseImageSampler(void) const;
  
    /** Method to set the image sampler. The image sampler is only used when
     * the metric is of type AdvancedMetricType, and has UseImageSampler set
     * to true. In other cases, the function does nothing.
     */
    virtual void
    SetAdvancedMetricImageSampler(ImageSamplerBaseType * sampler);
  
    /** Methods to get the image sampler. The image sampler is only used when
     * the metric is of type AdvancedMetricType, and has UseImageSampler set
     * to true. In other cases, the function returns 0.
     */
    virtual ImageSamplerBaseType *
    GetAdvancedMetricImageSampler(void) const;
  
    /** Get if the exact metric value is computed */
    virtual bool
    GetShowExactMetricValue(void) const
    {
      return this->m_ShowExactMetricValue;
    }
  
    /** Get the last computed exact metric value */
    virtual MeasureType
    GetCurrentExactMetricValue(void) const
    {
      return this->m_CurrentExactMetricValue;
    }
  
  protected:
    /** The parameters type. */
    typedef typename ITKBaseType::ParametersType ParametersType;
  
    /** The full sampler used by the GetExactValue method. */
    typedef itk::ImageGridSampler<FixedImageType>                       ExactMetricImageSamplerType;
    typedef typename ExactMetricImageSamplerType::Pointer               ExactMetricImageSamplerPointer;
    typedef typename ExactMetricImageSamplerType::SampleGridSpacingType ExactMetricSampleGridSpacingType;
  
    /** The constructor. */
    MetricBase();
    /** The destructor. */
    ~MetricBase() override = default;
  
    /**  Get the exact value. Mutual information computed over all points.
     * It is meant in situations when you optimize using just a subset of pixels,
     * but are interested in the exact value of the metric.
     *
     * This method only works when the itkYourMetric inherits from
     * the AdvancedMetricType.
     * In other cases it returns 0. You may re-implement this method in
     * the elxYourMetric, if you like.
     */
    virtual MeasureType
    GetExactValue(const ParametersType & parameters);
  
    /** \todo the method GetExactDerivative could as well be added here. */
  
    bool                             m_ShowExactMetricValue;
    ExactMetricImageSamplerPointer   m_ExactMetricSampler;
    MeasureType                      m_CurrentExactMetricValue;
    ExactMetricSampleGridSpacingType m_ExactMetricSampleGridSpacing;
    unsigned int                     m_ExactMetricEachXNumberOfIterations;
  
  private:
    /** The deleted copy constructor. */
    MetricBase(const Self &) = delete;
    /** The deleted assignment operator. */
    void
    operator=(const Self &) = delete;
  };
  
  } // end namespace elastix
  
  #ifndef ITK_MANUAL_INSTANTIATION
  #  include "elxMetricBase.hxx"
  #endif
  
  #endif // end #ifndef elxMetricBase_h
  