/*=========================================================================
 *
 *  Copyright Insight Software Consortium
 *
 *  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 itkGradientMagnitudeImageFilter_h
#define itkGradientMagnitudeImageFilter_h

#include "itkImageToImageFilter.h"

namespace itk
{
/** \class GradientMagnitudeImageFilter
 * \brief Computes the gradient magnitude of an image region at each pixel.
 *
 * \ingroup GradientFilters
 *
 * \sa Image
 * \sa Neighborhood
 * \sa NeighborhoodOperator
 * \sa NeighborhoodIterator
 * \ingroup ITKImageGradient
 *
 * \wiki
 * \wikiexample{EdgesAndGradients/GradientMagnitudeImageFilter,Compute the gradient magnitude image}
 * \endwiki
 */
template< typename TInputImage, typename TOutputImage >
class ITK_TEMPLATE_EXPORT GradientMagnitudeImageFilter:
  public ImageToImageFilter< TInputImage, TOutputImage >
{
public:
  ITK_DISALLOW_COPY_AND_ASSIGN(GradientMagnitudeImageFilter);

  /** Standard class type aliases. */
  using Self = GradientMagnitudeImageFilter;
  using Superclass = ImageToImageFilter< TInputImage, TOutputImage >;
  using Pointer = SmartPointer< Self >;
  using ConstPointer = SmartPointer< const Self >;

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

  /** Run-time type information (and related methods) */
  itkTypeMacro(GradientMagnitudeImageFilter, ImageToImageFilter);

  /** Extract some information from the image types.  Dimensionality
   * of the two images is assumed to be the same. */
  using OutputPixelType = typename TOutputImage::PixelType;
  using InputPixelType = typename TInputImage::PixelType;
  using RealType = typename NumericTraits< InputPixelType >::RealType;

  /** Extract some information from the image types.  Dimensionality
   * of the two images is assumed to be the same. */
  static constexpr unsigned int ImageDimension = TOutputImage::ImageDimension;

  /** Image type alias support */
  using InputImageType = TInputImage;
  using OutputImageType = TOutputImage;
  using InputImagePointer = typename InputImageType::Pointer;
  using OutputImagePointer = typename OutputImageType::Pointer;

  /** Superclass type alias. */
  using OutputImageRegionType = typename Superclass::OutputImageRegionType;

  /** GradientMagnitudeImageFilter needs a larger input requested
   * region than the output requested region (larger by the kernel
   * size to calculate derivatives).  As such,
   * GradientMagnitudeImageFilter needs to provide an implementation
   * for GenerateInputRequestedRegion() in order to inform the
   * pipeline execution model.
   *
   * \sa ImageToImageFilter::GenerateInputRequestedRegion() */
  void GenerateInputRequestedRegion() override;

  /** Use the image spacing information in calculations. Use this option if you
   *  want derivatives in physical space. Default is UseImageSpacingOn. */
  void SetUseImageSpacingOn()
  { this->SetUseImageSpacing(true); }

  /** Ignore the image spacing. Use this option if you want derivatives in
      isotropic pixel space.  Default is UseImageSpacingOn. */
  void SetUseImageSpacingOff()
  { this->SetUseImageSpacing(false); }

  /** Set/Get whether or not the filter will use the spacing of the input
      image in its calculations */
  itkSetMacro(UseImageSpacing, bool);
  itkGetConstMacro(UseImageSpacing, bool);

#ifdef ITK_USE_CONCEPT_CHECKING
  // Begin concept checking
  itkConceptMacro( InputHasNumericTraitsCheck,
                   ( Concept::HasNumericTraits< InputPixelType > ) );
  // End concept checking
#endif

protected:
  GradientMagnitudeImageFilter()
  {
    m_UseImageSpacing = true;
    this->DynamicMultiThreadingOn();
  }

  ~GradientMagnitudeImageFilter() override = default;

  /** GradientMagnitudeImageFilter can be implemented as a
   * multithreaded filter.  Therefore, this implementation provides a
   * DynamicThreadedGenerateData() routine which is called for each
   * processing thread. The output image data is allocated
   * automatically by the superclass prior to calling
   * DynamicThreadedGenerateData().  DynamicThreadedGenerateData can only write to
   * the portion of the output image specified by the parameter
   * "outputRegionForThread"
   *
   * \sa ImageToImageFilter::ThreadedGenerateData(),
   *     ImageToImageFilter::GenerateData() */
  void DynamicThreadedGenerateData(const OutputImageRegionType & outputRegionForThread) override;


  void PrintSelf(std::ostream &, Indent) const override;

private:
  bool m_UseImageSpacing;
};
} // end namespace itk

#ifndef ITK_MANUAL_INSTANTIATION
#include "itkGradientMagnitudeImageFilter.hxx"
#endif

#endif
