itkNthElementPixelAccessor.h

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/*=========================================================================
 *
 *  Copyright NumFOCUS
 *
 *  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
 *
 *         https://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 itkNthElementPixelAccessor_h
#define itkNthElementPixelAccessor_h
 
#include "itkMacro.h"
#include "itkDefaultConvertPixelTraits.h"
#include "itkVariableLengthVector.h"
#include "itkDefaultVectorPixelAccessor.h"
 
namespace itk
{
 
template <typename T, typename TContainer>
class NthElementPixelAccessor
{
public:
  using Self = NthElementPixelAccessor;

  using ExternalType = T;

  using InternalType = TContainer;

  inline void
  Set(InternalType & output, const ExternalType & input) const
  {
    DefaultConvertPixelTraits<InternalType>::SetNthComponent(m_ElementNumber, output, input);
  }

  [[nodiscard]] inline ExternalType
  Get(const InternalType & input) const
  {
    return static_cast<ExternalType>(DefaultConvertPixelTraits<InternalType>::GetNthComponent(m_ElementNumber, input));
  }

  [[nodiscard]] unsigned int
  GetElementNumber() const
  {
    return m_ElementNumber;
  }

  void
  SetElementNumber(unsigned int nth)
  {
    m_ElementNumber = nth;
  }

  bool
  operator==(const Self & accessor) const
  {
    return m_ElementNumber == accessor.m_ElementNumber;
  }
 
  ITK_UNEQUAL_OPERATOR_MEMBER_FUNCTION(Self);

  NthElementPixelAccessor &
  operator=(const NthElementPixelAccessor & accessor) = default;

  NthElementPixelAccessor() = default;
 
private:
  // Identifier of the N-th element to be accessed
  unsigned int m_ElementNumber{ 0 };
};
 
 
template <typename TOutputPixelType, typename TPixelType>
class NthElementPixelAccessor<TOutputPixelType, itk::VariableLengthVector<TPixelType>>
  : private DefaultVectorPixelAccessor<TPixelType>
{
public:
  using Self = NthElementPixelAccessor;
 
  using VectorLengthType = unsigned int;

  using ExternalType = TOutputPixelType;

  using InternalType = TPixelType;
 
  using ActualPixelType = VariableLengthVector<TPixelType>;
 
  inline void
  Set(ActualPixelType & output, const ExternalType & input) const
  {
    output[m_ElementNumber] = input;
  }
 
  inline void
  Set(InternalType & output, const ExternalType & input, const SizeValueType offset) const
  {
    // note: v is a reference to the internal buffer, this method of
    // access relies on return value optimization to work
    ActualPixelType v = Superclass::Get(output, offset);
 
    return Set(v, input);
  }
 
  [[nodiscard]] inline ExternalType
  Get(const ActualPixelType & input) const
  {
    const auto output = static_cast<ExternalType>(input[m_ElementNumber]);
    return output;
  }
 
  [[nodiscard]] inline ExternalType
  Get(const InternalType & input, const SizeValueType offset) const
  {
    return Get(Superclass::Get(input, offset));
  }
 

  [[nodiscard]] unsigned int
  GetElementNumber() const
  {
    return m_ElementNumber;
  }

  void
  SetElementNumber(unsigned int nth)
  {
    m_ElementNumber = nth;
  }

  void
  SetVectorLength(VectorLengthType l)
  {
    Superclass::SetVectorLength(l);
  }

  [[nodiscard]] VectorLengthType
  GetVectorLength() const
  {
    return Superclass::GetVectorLength();
  }
 
  NthElementPixelAccessor(unsigned int length = 1) { Superclass::SetVectorLength(length); }

  bool
  operator==(const Self & accessor) const
  {
    return m_ElementNumber == accessor.m_ElementNumber;
  }
 
  ITK_UNEQUAL_OPERATOR_MEMBER_FUNCTION(Self);

  NthElementPixelAccessor &
  operator=(const NthElementPixelAccessor & accessor)
  {
    m_ElementNumber = accessor.m_ElementNumber;
    this->SetVectorLength(accessor.GetVectorLength());
    return *this;
  }
 
protected:
  using Superclass = DefaultVectorPixelAccessor<TPixelType>;
 
private:
  VectorLengthType m_ElementNumber{ 0 };
};
 
} // end namespace itk
 
#endif