itkLabelObjectAccessors.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 itkLabelObjectAccessors_h
#define itkLabelObjectAccessors_h
 
#include "itkMacro.h"
 
/*
 *
 * This code was contributed in the Insight Journal paper:
 * "Label object representation and manipulation with ITK"
 * by Lehmann G.
 * https://doi.org/10.54294/q6auw4
 *
 */
 
namespace itk
{
namespace Functor
{
template <typename TLabelObject>
class LabelLabelObjectAccessor
{
public:
  using LabelObjectType = TLabelObject;
  using AttributeValueType = typename LabelObjectType::LabelType;
 
  inline AttributeValueType
  operator()(const LabelObjectType * labelObject) const
  {
    return labelObject->GetLabel();
  }
};
 
template <typename TLabelObject>
class NumberOfLinesLabelObjectAccessor
{
public:
  using LabelObjectType = TLabelObject;
  using AttributeValueType = int;
 
  inline AttributeValueType
  operator()(const LabelObjectType * labelObject) const
  {
    return labelObject->GetNumberOfLines();
  }
};
 
template <typename TLabelObject, typename TAttributeAccessor>
class LabelObjectComparator
{
public:
  using LabelObjectType = TLabelObject;
  using AttributeAccessorType = TAttributeAccessor;
  bool
  operator()(const LabelObjectType * a, const LabelObjectType * b) const
  {
    return m_Accessor(a) > m_Accessor(b);
  }
 
  LabelObjectComparator() = default;
  LabelObjectComparator(LabelObjectComparator const & from) { m_Accessor = from.m_Accessor; }
 
private:
  AttributeAccessorType m_Accessor;
};
 
template <typename TLabelObject, typename TAttributeAccessor>
class LabelObjectReverseComparator
{
public:
  using LabelObjectType = TLabelObject;
  using AttributeAccessorType = TAttributeAccessor;
  bool
  operator()(const LabelObjectType * a, const LabelObjectType * b) const
  {
    return m_Accessor(a) < m_Accessor(b);
  }
 
  LabelObjectReverseComparator() = default;
  LabelObjectReverseComparator(LabelObjectReverseComparator const & from) { m_Accessor = from.m_Accessor; }
 
private:
  AttributeAccessorType m_Accessor;
};
} // namespace Functor
} // end namespace itk
 
#endif