/*=========================================================================
 *
 *  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 itkLaplacianImageFilter_h
#define itkLaplacianImageFilter_h

#include "itkImageToImageFilter.h"

namespace itk
{
/**
 * \class LaplacianImageFilter
 *
 * This filter computes the Laplacian of a scalar-valued image. The Laplacian
 * is an isotropic measure of the 2nd spatial derivative of an image. The
 * Laplacian of an image highlights regions of rapid intensity change and is
 * therefore often used for edge detection.  Often, the Laplacian is applied to
 * an image that has first been smoothed with a Gaussian filter in order to
 * reduce its sensitivity to noise.
 *
 * \par
 * The Laplacian at each pixel location is computed by convolution with the
 * itk::LaplacianOperator.
 *
 * \par Inputs and Outputs
 * The input to this filter is a scalar-valued itk::Image of arbitrary
 * dimension. The output is a scalar-valued itk::Image.
 *
 * \warning The pixel type of the input and output images must be of real type
 * (float or double). ConceptChecking is used here to enforce the input pixel
 * type. You will get a compilation error if the pixel type of the input and
 * output images is not float or double.
 *
 * \sa Image
 * \sa Neighborhood
 * \sa NeighborhoodOperator
 * \sa NeighborhoodIterator
 * \sa LaplacianOperator
 *
 * \ingroup ImageFeatureExtraction
 * \ingroup ITKImageFeature
 *
 * \wiki
 * \wikiexample{ImageProcessing/LaplacianImageFilter,Compute the Laplacian of an image}
 * \endwiki
 */
template< typename TInputImage, typename TOutputImage >
class LaplacianImageFilter:
  public ImageToImageFilter< TInputImage, TOutputImage >
{
public:
  /** Standard "Self" & Superclass typedef.   */
  typedef LaplacianImageFilter                            Self;
  typedef ImageToImageFilter< TInputImage, TOutputImage > Superclass;

  /** Extract some information from the image types.  Dimensionality
   * of the two images is assumed to be the same. */
  typedef typename TOutputImage::PixelType         OutputPixelType;
  typedef typename TOutputImage::InternalPixelType OutputInternalPixelType;
  typedef typename TInputImage::PixelType          InputPixelType;
  typedef typename TInputImage::InternalPixelType  InputInternalPixelType;
  itkStaticConstMacro(InputImageDimension, unsigned int,
                      TInputImage::ImageDimension);
  itkStaticConstMacro(ImageDimension, unsigned int,
                      TOutputImage::ImageDimension);

  /** Image typedef support. */
  typedef TInputImage                      InputImageType;
  typedef TOutputImage                     OutputImageType;
  typedef typename InputImageType::Pointer InputImagePointer;

  /** Smart pointer typedef support.   */
  typedef SmartPointer< Self >       Pointer;
  typedef SmartPointer< const Self > ConstPointer;

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

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

  /** LaplacianImageFilter needs a larger input requested region than
   * the output requested region (larger in the direction of the
   * derivative).  As such, LaplacianImageFilter needs to provide an
   * implementation for GenerateInputRequestedRegion() in order to
   * inform the pipeline execution model.
   *
   * \sa ImageToImageFilter::GenerateInputRequestedRegion()  */
  virtual void GenerateInputRequestedRegion() ITK_OVERRIDE;

 /** Enable/Disable using the image spacing information in
   *  calculations. Use this option if you  want derivatives in
   *  physical space. Default  is UseImageSpacingOn. */
  itkBooleanMacro( UseImageSpacing );

  /** 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( SameDimensionCheck,
                   ( Concept::SameDimension< InputImageDimension, ImageDimension > ) );
  itkConceptMacro( InputPixelTypeIsFloatingPointCheck,
                   ( Concept::IsFloatingPoint< InputPixelType > ) );
  itkConceptMacro( OutputPixelTypeIsFloatingPointCheck,
                   ( Concept::IsFloatingPoint< OutputPixelType > ) );
  // End concept checking
#endif

protected:
  LaplacianImageFilter()
  {
    m_UseImageSpacing = true;
  }

  virtual ~LaplacianImageFilter()  {}

  /** Standard pipeline method. While this class does not implement a
   * ThreadedGenerateData(), its GenerateData() delegates all
   * calculations to an NeighborhoodOperatorImageFilter.  Since the
   * NeighborhoodOperatorImageFilter is multithreaded, this filter is
   * multithreaded by default.   */
  void GenerateData() ITK_OVERRIDE;

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

private:
  LaplacianImageFilter(const Self &) ITK_DELETE_FUNCTION;
  void operator=(const Self &) ITK_DELETE_FUNCTION;

  bool m_UseImageSpacing;
};
} // end namespace itk

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

#endif
