/*=========================================================================
 *
 *  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 itkZeroCrossingBasedEdgeDetectionImageFilter_h
#define itkZeroCrossingBasedEdgeDetectionImageFilter_h

#include "itkImageToImageFilter.h"
#include "itkImage.h"

namespace itk
{
/** \class ZeroCrossingBasedEdgeDetectionImageFilter
 * \brief This filter implements a zero-crossing based edge detecor.
 *
 * The zero-crossing based edge detector looks for pixels in the Laplacian of
 * an image where the value of the Laplacian passes through zero --- points
 * where the Laplacian changes sign.  Such points often occur at "edges" in
 * images --- i.e. points where the intensity of the image changes rapidly,
 * but they also occur at places that are not as easy to associate with edges.
 * It is best to think of the zero crossing detector as some sort of feature
 * detector rather than as a specific edge detector.
 *
 * \par
 * Zero crossings always lie on closed contours and so the output from the zero
 * crossing detector is usually a binary image with single pixel thickness
 * lines showing the positions of the zero crossing points.
 *
 * \par
 * In this implementation, the input image is first smoothed with a Gaussian
 * filter, then the LaplacianImageFilter is applied to smoothed image. Finally
 * the zero-crossing of the Laplacian of the smoothed image is detected. The
 * output is a binary image.
 *
 * \par Inputs and Outputs
 * The input to the filter should be a scalar, itk::Image of arbitrary
 * dimension.  The output image is a binary, labeled image.  See
 * itkZeroCrossingImageFilter for more information on requirements of the data
 * type of the output.
 *
 * \par
 * To use this filter, first set the parameters (variance and maximum error)
 * needed by the embedded DiscreteGaussianImageFilter, i.e.  See
 * DiscreteGaussianImageFilter for information about these parameters.
 * Optionally, you may also set foreground and background values for the
 * zero-crossing filter.  The default label values are Zero for the background
 * and One for the foreground, as defined in NumericTraits for the data type of
 * the output image.
 *
 * \sa DiscreteGaussianImageFilter
 * \sa LaplacianImageFilter
 * \sa ZeroCrossingImageFilter
 * \ingroup ImageFeatureExtraction
 * \ingroup ITKImageFeature
 */
template< typename TInputImage, typename TOutputImage >
class ITK_TEMPLATE_EXPORT ZeroCrossingBasedEdgeDetectionImageFilter:
  public ImageToImageFilter< TInputImage, TOutputImage >
{
public:
  ITK_DISALLOW_COPY_AND_ASSIGN(ZeroCrossingBasedEdgeDetectionImageFilter);

  /** Standard "Self" & Superclass type alias.   */
  using Self = ZeroCrossingBasedEdgeDetectionImageFilter;
  using Superclass = ImageToImageFilter< TInputImage, TOutputImage >;

  /** Image type alias support   */
  using InputImageType = TInputImage;
  using OutputImageType = TOutputImage;

  /** SmartPointer type alias support  */
  using Pointer = SmartPointer< Self >;
  using ConstPointer = SmartPointer< const Self >;

  /** Define pixel type  */
  using InputImagePixelType = typename TInputImage::PixelType;
  using OutputImagePixelType = typename TOutputImage::PixelType;

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

  /** Typedef to describe the output image region type. */
  using OutputImageRegionType = typename TOutputImage::RegionType;

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

  /** ImageDimension enumeration   */
  static constexpr unsigned int ImageDimension = TInputImage::ImageDimension;
  static constexpr unsigned int OutputImageDimension = TOutputImage::ImageDimension;

  /** Typedef of double containers */
  using ArrayType = FixedArray< double, Self::ImageDimension >;

  /** Standard get/set macros for Gaussian filter parameters.  */
  itkSetMacro(Variance, ArrayType);
  itkGetConstMacro(Variance, const ArrayType);
  itkSetMacro(MaximumError, ArrayType);
  itkGetConstMacro(MaximumError, const ArrayType);

  /** Get/Set the label values for the ZeroCrossingImageFilter */
  itkGetConstMacro(BackgroundValue, OutputImagePixelType);
  itkSetMacro(BackgroundValue, OutputImagePixelType);
  itkGetConstMacro(ForegroundValue, OutputImagePixelType);
  itkSetMacro(ForegroundValue, OutputImagePixelType);

  /** Set the variance parameter needed by the embedded gaussian filter  */
  void SetVariance(const typename ArrayType::ValueType v)
  {
    m_Variance.Fill(v);
  }

  /** Set the MaximumError parameter needed by the embedded gaussian filter
 * This value is used to set the desired maximum error of the gaussian
 * approximation.  Maximum error is the difference between the area under the
 * discrete Gaussian curve and the area under the continuous Gaussian.  Maximum
 * error affects the Gaussian operator size. The value must be between 0.0 and
 * 1.0. */
  void SetMaximumError(const typename ArrayType::ValueType v)
  {
    m_MaximumError.Fill(v);
  }

#ifdef ITK_USE_CONCEPT_CHECKING
  // Begin concept checking
  itkConceptMacro( OutputEqualityComparableCheck,
                   ( Concept::EqualityComparable< OutputImagePixelType > ) );
  itkConceptMacro( SameDimensionCheck,
                   ( Concept::SameDimension< ImageDimension, OutputImageDimension > ) );
  itkConceptMacro( SameTypeCheck,
                   ( Concept::SameType< InputImagePixelType, OutputImagePixelType > ) );
  itkConceptMacro( OutputOStreamWritableCheck,
                   ( Concept::OStreamWritable< OutputImagePixelType > ) );
  itkConceptMacro( PixelTypeIsFloatingPointCheck,
                   ( Concept::IsFloatingPoint< InputImagePixelType > ) );
  // End concept checking
#endif

protected:
  ZeroCrossingBasedEdgeDetectionImageFilter()
  {
    m_Variance.Fill(1.0);
    m_MaximumError.Fill(0.01);
    m_BackgroundValue = NumericTraits< OutputImagePixelType >::ZeroValue();
    m_ForegroundValue = NumericTraits< OutputImagePixelType >::OneValue();
  }

  ~ZeroCrossingBasedEdgeDetectionImageFilter() override = default;
  void PrintSelf(std::ostream & os, Indent indent) const override;

  /** Standard pipeline method. While this class does not implement a
   * ThreadedGenerateData(), its GenerateData() delegates all
   * calculations to the pipeline of a DiscreteGaussianImageFilter,
   * a LaplacianImageFilter and a ZeroCrossingImageFilter.  Since these
   * filters are multithreaded, this filter is multithreaded by default.
   */
  void GenerateData() override;

private:
  /** The variance of the Gaussian Filter used in this filter */
  ArrayType m_Variance;

  /** The maximum error of the gaussian blurring kernel in each dimensional
   * direction.  */
  ArrayType m_MaximumError;

  OutputImagePixelType m_BackgroundValue;
  OutputImagePixelType m_ForegroundValue;
};
} //end of namespace itk

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

#endif
