text: /*=========================================================================
   *
   *  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 itkChainCodePath2D_h
  #define itkChainCodePath2D_h
  
  #include "itkChainCodePath.h"
  #include "itkIndex.h"
  
  #include <vector>
  #include <string>
  
  namespace itk
  {
  /** \class ChainCodePath2D
   * \brief  Represent a 2D path as a sequence of connected image index offsets
   *
   * This class is intended to represent sequences of connected indices in a 2D
   * image plane.  It does so by storing the offset of each index from its
   * immediately preceding, connected, index using a standard Freeman code
   * (1=up, 2=up to the right, and so on proceeding clockwise to 8=up
   * to the left).  The only image index stored directly is thatof the first
   * index.
   * ChainCodePath2D maps a 1D integer input (step number) to
   * a 2D integer output (either an offset or an image index, depending on
   * whether Evaluate or EvaluateToIndex is called).
   *
   * \sa ChainCodePath
   * \sa ParametricPath
   * \sa Path
   * \sa Index
   *
   * \ingroup PathObjects
   * \ingroup ITKPath
   */
  class ITK_TEMPLATE_EXPORT ChainCodePath2D : public ChainCodePath<2>
  {
  public:
    ITK_DISALLOW_COPY_AND_ASSIGN(ChainCodePath2D);
  
    /** Dimension underlying input image. */
    static constexpr unsigned int Dimension = 2;
  
    /** Standard class type aliases. */
    using Self = ChainCodePath2D;
    using Superclass = ChainCodePath<2>;
  
    using Pointer = SmartPointer<Self>;
    using ConstPointer = SmartPointer<const Self>;
  
    /** Run-time type information (and related methods). */
    itkTypeMacro(ChainCodePath2D, ChainCodePath);
  
    /** OutputType type alias support */
    using OutputType = Superclass::OutputType;
    using InputType = Superclass::InputType;
  
    /** The output type of this function is an Index */
    using OffsetType = OutputType;
    using IndexType = Index<2>;
  
    /** ChainCodeType is a usless relic of the parent class */
    using ChainCodeType = Superclass::ChainCodeType;
    using ChainCodeSizeType = Superclass::ChainCodeSizeType;
  
    /** ChainCodePath2D stores its data as a Freeman-encoded chain code */
    using ChainCode2DType = std::vector<int>;
  
    // Functions inherited from Path
  
    /** Evaluate the chaincode for the offset at the specified path-position. */
    OutputType
    Evaluate(const InputType & input) const override;
  
    /** Like Evaluate(), but returns the index at the specified path-position. */
    IndexType
    EvaluateToIndex(const InputType & input) const override;
  
    /** Increment the input variable passed by reference and return the offset
     * stored at the previous path-position.  If the chaincode is unable to be
     * incremented, input is not changed and an offset of zero is returned, which
     * may be used to check for the end of the chain code. */
    OffsetType
    IncrementInput(InputType & input) const override;
  
    // Functions specific to ChainCodePath and its descendents
  
    /** New() method for dynamic construction */
    itkNewMacro(Self);
  
    /** How many steps in the chaincode? */
    ChainCodeSizeType
    NumberOfSteps() const override
    {
      return m_Chain2D.size();
    }
  
    /** Insert a new step into the chaincode at a specified position */
    inline void
    InsertStep(InputType position, int encodedStep)
    {
      m_Chain2D.insert(m_Chain2D.begin() + position, encodedStep);
      this->Modified();
    }
  
    void
    InsertStep(InputType position, OffsetType step) override
    {
      m_Chain2D.insert(m_Chain2D.begin() + position, EncodeOffset(step));
      this->Modified();
    }
  
    /** Change the direction of a step in the chaincode */
    inline void
    ChangeStep(InputType position, int encodedStep)
    {
      m_Chain2D[position] = encodedStep;
      this->Modified();
    }
  
    void
    ChangeStep(InputType position, OffsetType step) override
    {
      m_Chain2D[position] = EncodeOffset(step);
      this->Modified();
    }
  
    /** Remove all steps from the chain code */
    void
    Clear() override
    {
      m_Chain2D.clear();
      this->Modified();
    }
  
    std::string
    GetChainCodeAsString() const;
  
  protected:
    ChainCodePath2D();
    ~ChainCodePath2D() override;
    void
    PrintSelf(std::ostream & os, Indent indent) const override;
  
    /** Encode and Decode between an offset and a Freeman code */
    inline int
    EncodeOffset(OffsetType step) const
    {
      return m_FreemanCode[step[0] + 1][step[1] + 1];
    }
  
    inline OffsetType
    DecodeOffset(int encodedStep) const
    {
      return m_ReverseFreemanCode[encodedStep];
    }
  
  private:
    ChainCode2DType m_Chain2D; // the Freeman-encoded chain code
  
    // FreemanCode[][] implements a lookup table for converting offsets to a
    // Freeman code.  Within each dimension, the only allowable offset values are
    // { -1, 0, 1 }.  The y-axis is assumed to point up.  It is initialized in the
    // constructor.  Use it as follows:
    //
    //   encodedValue = m_FreemanCode[ x offset + 1 ][ y offset + 1 ]
    //
    int m_FreemanCode[3][3];
  
    // m_ReverseFreemanCode[ encodedValue ] implements a lookup table for the
    // inverse of m_FreemanCode[][].  It is initialized in the constructor.
    OffsetType m_ReverseFreemanCode[9];
  };
  } // end namespace itk
  
  #endif
  