itkGradientImageFilter.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 itkGradientImageFilter_h
#define itkGradientImageFilter_h
 
#include "itkImageToImageFilter.h"
#include "itkCovariantVector.h"
#include "itkImageRegionIterator.h"
#include "itkZeroFluxNeumannBoundaryCondition.h"
#include <memory> // For unique_ptr.
 
namespace itk
{
 
 
template <typename TPixelType, unsigned int VImageDimension>
class VectorImage;
 

template <typename TInputImage,
          typename TOperatorValueType = float,
          typename TOutputValueType = float,
          typename TOutputImageType =
            Image<CovariantVector<TOutputValueType, TInputImage::ImageDimension>, TInputImage::ImageDimension>>
class ITK_TEMPLATE_EXPORT GradientImageFilter : public ImageToImageFilter<TInputImage, TOutputImageType>
{
public:
  ITK_DISALLOW_COPY_AND_MOVE(GradientImageFilter);

  static constexpr unsigned int InputImageDimension = TInputImage::ImageDimension;
  static constexpr unsigned int OutputImageDimension = TOutputImageType::ImageDimension;

  using InputImageType = TInputImage;
  using InputImagePointer = typename InputImageType::Pointer;
  using OutputImageType = TOutputImageType;
  using OutputImagePointer = typename OutputImageType::Pointer;

  using Self = GradientImageFilter;
  using Superclass = ImageToImageFilter<InputImageType, OutputImageType>;
  using Pointer = SmartPointer<Self>;
  using ConstPointer = SmartPointer<const Self>;

  itkNewMacro(Self);

  itkOverrideGetNameOfClassMacro(GradientImageFilter);

  using InputPixelType = typename InputImageType::PixelType;
  using OperatorValueType = TOperatorValueType;
  using OutputValueType = TOutputValueType;
  using OutputPixelType = typename OutputImageType::PixelType;
  using CovariantVectorType = CovariantVector<OutputValueType, Self::OutputImageDimension>;
  using OutputImageRegionType = typename OutputImageType::RegionType;

  void
  GenerateInputRequestedRegion() override;

  itkSetMacro(UseImageSpacing, bool);
  itkGetConstMacro(UseImageSpacing, bool);
  itkBooleanMacro(UseImageSpacing);
#if !defined(ITK_FUTURE_LEGACY_REMOVE)
  void
  SetUseImageSpacingOn()
  {
    this->SetUseImageSpacing(true);
  }

  void
  SetUseImageSpacingOff()
  {
    this->SetUseImageSpacing(false);
  }
#endif

  void
  OverrideBoundaryCondition(ImageBoundaryCondition<TInputImage> * boundaryCondition);
 
  itkConceptMacro(InputConvertibleToOutputCheck, (Concept::Convertible<InputPixelType, OutputValueType>));
  itkConceptMacro(OutputHasNumericTraitsCheck, (Concept::HasNumericTraits<OutputValueType>));

  itkSetMacro(UseImageDirection, bool);
  itkGetConstMacro(UseImageDirection, bool);
  itkBooleanMacro(UseImageDirection);
protected:
  GradientImageFilter();
  ~GradientImageFilter() override = default;
  void
  PrintSelf(std::ostream & os, Indent indent) const override;

  void
  DynamicThreadedGenerateData(const OutputImageRegionType & outputRegionForThread) override;
 
 
private:
  void
  GenerateOutputInformation() override;
 
  // An overloaded method which may transform the gradient to a
  // physical vector and converts to the correct output pixel type.
  template <typename TValue>
  void
  SetOutputPixel(ImageRegionIterator<VectorImage<TValue, OutputImageDimension>> & it, CovariantVectorType & gradient)
  {
    if (this->m_UseImageDirection)
    {
      CovariantVectorType physicalGradient;
      it.GetImage()->TransformLocalVectorToPhysicalVector(gradient, physicalGradient);
      it.Set(OutputPixelType(physicalGradient.GetDataPointer(), InputImageDimension, false));
    }
    else
    {
      it.Set(OutputPixelType(gradient.GetDataPointer(), InputImageDimension, false));
    }
  }
 
  template <typename T>
  void
  SetOutputPixel(ImageRegionIterator<T> & it, CovariantVectorType & gradient)
  {
    // This uses the more efficient set by reference method
    if (this->m_UseImageDirection)
    {
      it.GetImage()->TransformLocalVectorToPhysicalVector(gradient, it.Value());
    }
    else
    {
      it.Value() = gradient;
    }
  }
 
 
  bool m_UseImageSpacing{ true };
 
  // flag to take or not the image direction into account
  // when computing the derivatives.
  bool m_UseImageDirection{ true };
 
  // allow setting the the m_BoundaryCondition
  std::unique_ptr<ImageBoundaryCondition<TInputImage, TInputImage>> m_BoundaryCondition{
    std::make_unique<ZeroFluxNeumannBoundaryCondition<TInputImage>>()
  };
};
} // end namespace itk
 
#ifndef ITK_MANUAL_INSTANTIATION
#  include "itkGradientImageFilter.hxx"
#endif
 
#endif