/*=========================================================================
 *
 *  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 itkHardConnectedComponentImageFilter_h
#define itkHardConnectedComponentImageFilter_h

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

namespace itk
{
/**
 * \class HardConnectedComponentImageFilter
 * The purpose of this program is to produce the connected components
 * for any input binary image of dimensionality n.
 *
 * The program does a forward pass line by line through the entire image.
 * Each cell in the foreground is assigned the same label value as cells
 * in its neighborhood. If there is no label among the cells in its neighborhood,
 * a new label value is assigned to the cell. This means that this cell belongs
 * to a different connected component. We set up an equivalence table for each
 * label to indicate the equivalence of the labels stored in the table. After
 * the forward pass goes through the entire image, we merge the different
 * connected components corresponding to the equivalence labels in the table.
 * We implement this strategy in the function GenerateData().
 *
 * There are two options in the program.
 * 1. Take an nD binary image as input, and produce an nD gray image, where intensity indicates label assigned to a connected component.
 * 2. Take an nD binary image and a set of seed points as input, and output an nD binary image containing the cells connected to the seeds.
 *    For option 2, users need to assign the member variable std::list<IndexType> m_Seeds before calling function GenerateData().
 * \sa ImageToImageFilter
 * \ingroup ITKConnectedComponents
 */
template< typename TInputImage, typename TOutputImage >
class ITK_TEMPLATE_EXPORT HardConnectedComponentImageFilter:
  public ImageToImageFilter< TInputImage, TOutputImage >
{
public:
  ITK_DISALLOW_COPY_AND_ASSIGN(HardConnectedComponentImageFilter);

  /**
   * Standard class typedef's
   */
  using Self = HardConnectedComponentImageFilter;
  using Superclass = ImageToImageFilter< TInputImage, TOutputImage >;
  using Pointer = SmartPointer< Self >;
  using ConstPointer = SmartPointer< const Self >;

  /**
   * Extract some information from the image types.  Dimensionality
   * of the two images is assumed to be the same.
   */
  using OutputPixelType = typename TOutputImage::PixelType;
  using OutputInternalPixelType = typename TOutputImage::InternalPixelType;
  using InputPixelType = typename TInputImage::PixelType;
  using InputInternalPixelType = typename TInputImage::InternalPixelType;
  static constexpr unsigned int InputImageDimension = TInputImage::ImageDimension;
  static constexpr unsigned int ImageDimension = TOutputImage::ImageDimension;

  /**
   * Image type alias support
   */
  using InputImageType = TInputImage;
  using OutputImageType = TOutputImage;
  using IndexType = typename TInputImage::IndexType;
  using SizeType = typename TInputImage::SizeType;
  using RegionType = typename TOutputImage::RegionType;
  using ListType = std::list< IndexType >;

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

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

  /** Setting the seed points for specified object. */
  void SetObjectSeed(const IndexType & seed)
  { m_Seeds.push_front(seed); }

#ifdef ITK_USE_CONCEPT_CHECKING
  // Begin concept checking
  itkConceptMacro( SameDimensionCheck,
                   ( Concept::SameDimension< InputImageDimension, ImageDimension > ) );
  itkConceptMacro( IntConvertibleToOutputCheck,
                   ( Concept::Convertible< int, OutputPixelType > ) );
  itkConceptMacro( UnsignedShortConvertibleToOutputCheck,
                   ( Concept::Convertible< unsigned short, OutputPixelType > ) );
  itkConceptMacro( OutputEqualityComparableCheck,
                   ( Concept::EqualityComparable< OutputPixelType > ) );
  itkConceptMacro( UnsignedCharConvertibleToOutputCheck,
                   ( Concept::Convertible< unsigned char, OutputPixelType > ) );
  itkConceptMacro( OutputIncrementDecrementOperatorsCheck,
                   ( Concept::IncrementDecrementOperators< OutputPixelType > ) );
  // End concept checking
#endif

protected:
  HardConnectedComponentImageFilter() = default;
  ~HardConnectedComponentImageFilter() override = default;

  /**
   * Standard pipeline method.
   */
  void GenerateData() override;

  void PrintSelf(std::ostream & os, Indent indent) const override
  { Superclass::PrintSelf(os, indent); }

private:
  ListType m_Seeds;
};
} // end namespace itk

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

#endif
