itkCentralDifferenceImageFunction.h

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/*=========================================================================
 *
 *  Copyright NumFOCUS
 *
 *  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
 *
 *         https://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 itkCentralDifferenceImageFunction_h
#define itkCentralDifferenceImageFunction_h
 
#include "itkImageFunction.h"
#include "itkCovariantVector.h"
#include "itkInterpolateImageFunction.h"
#include "itkDefaultConvertPixelTraits.h"
 
namespace itk
{
template <typename TInputImage,
          typename TCoordinate = float,
          typename TOutputType = CovariantVector<double, TInputImage::ImageDimension>>
class ITK_TEMPLATE_EXPORT CentralDifferenceImageFunction : public ImageFunction<TInputImage, TOutputType, TCoordinate>
{
public:
  ITK_DISALLOW_COPY_AND_MOVE(CentralDifferenceImageFunction);

  static constexpr unsigned int ImageDimension = TInputImage::ImageDimension;

  using Self = CentralDifferenceImageFunction;
  using Superclass = ImageFunction<TInputImage, TOutputType, TCoordinate>;
  using Pointer = SmartPointer<Self>;
  using ConstPointer = SmartPointer<const Self>;

  itkOverrideGetNameOfClassMacro(CentralDifferenceImageFunction);

  itkNewMacro(Self);

  using InputImageType = TInputImage;

  using InputPixelType = typename InputImageType::PixelType;

  using InputPixelConvertType = DefaultConvertPixelTraits<InputPixelType>;

  using typename Superclass::OutputType;

  using OutputConvertType = DefaultConvertPixelTraits<OutputType>;

  using OutputValueType = typename OutputConvertType::ComponentType;

  using ScalarDerivativeType = CovariantVector<OutputValueType, Self::ImageDimension>;

  using typename Superclass::IndexType;

  using typename Superclass::ContinuousIndexType;

  using typename Superclass::PointType;

  using SpacingType = typename TInputImage::SpacingType;

  using InterpolatorType = InterpolateImageFunction<TInputImage, TCoordinate>;
  using InterpolatorPointer = typename InterpolatorType::Pointer;

  void
  SetInputImage(const TInputImage * inputData) override;

  virtual void
  SetInterpolator(InterpolatorType * interpolator);

  itkGetModifiableObjectMacro(Interpolator, InterpolatorType);

  OutputType
  EvaluateAtIndex(const IndexType & index) const override;

  OutputType
  Evaluate(const PointType & point) const override;

  OutputType
  EvaluateAtContinuousIndex(const ContinuousIndexType & cindex) const override;

  itkSetMacro(UseImageDirection, bool);
  itkGetConstMacro(UseImageDirection, bool);
  itkBooleanMacro(UseImageDirection);
 
protected:
  CentralDifferenceImageFunction();
  ~CentralDifferenceImageFunction() override = default;
  void
  PrintSelf(std::ostream & os, Indent indent) const override;
 
private:
  template <typename T>
  struct OutputTypeSpecializationStructType
  {
    using Type = T;
  };

  template <typename Type>
  inline void
  EvaluateAtIndexSpecialized(const IndexType & index,
                             OutputType &      orientedDerivative,
                             OutputTypeSpecializationStructType<OutputType>) const;

  template <typename Type>
  inline void
  EvaluateAtIndexSpecialized(const IndexType & index,
                             OutputType &      derivative,
                             OutputTypeSpecializationStructType<Type>) const;

  template <typename Type>
  inline void
  EvaluateAtContinuousIndexSpecialized(const ContinuousIndexType & cindex,
                                       OutputType &                orientedDerivative,
                                       OutputTypeSpecializationStructType<OutputType>) const;

  template <typename Type>
  inline void
  EvaluateAtContinuousIndexSpecialized(const ContinuousIndexType & cindex,
                                       OutputType &                derivative,
                                       OutputTypeSpecializationStructType<Type>) const;

  // NOTE: for some unknown reason, making these methods inline (as those above are inlined) makes them run *slower*.
  template <typename Type>
  void
  EvaluateSpecialized(const PointType & point,
                      OutputType &      orientedDerivative,
                      OutputTypeSpecializationStructType<OutputType>) const;

  template <typename Type>
  void
  EvaluateSpecialized(const PointType & point, OutputType & derivative, OutputTypeSpecializationStructType<Type>) const;
 
  // flag to take or not the image direction into account
  // when computing the derivatives.
  bool m_UseImageDirection{ true };
 
  // interpolator
  InterpolatorPointer m_Interpolator{};
};
} // end namespace itk
 
#ifndef ITK_MANUAL_INSTANTIATION
#  include "itkCentralDifferenceImageFunction.hxx"
#endif
 
#endif