itkConnectedComponentAlgorithm.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 itkConnectedComponentAlgorithm_h
#define itkConnectedComponentAlgorithm_h
 
#include "itkImage.h"
#include "itkShapedNeighborhoodIterator.h"
 
namespace itk
{
template <typename TIterator>
TIterator *
setConnectivity(TIterator * it, bool fullyConnected = false)
{
 
  it->ClearActiveList();
  if (!fullyConnected)
  {
    // only activate the neighbors that are face connected
    // to the current pixel. do not include the center pixel
    typename TIterator::OffsetType offset{};
    for (unsigned int d = 0; d < TIterator::Dimension; ++d)
    {
      offset[d] = -1;
      it->ActivateOffset(offset);
      offset[d] = 1;
      it->ActivateOffset(offset);
      offset[d] = 0;
    }
  }
  else
  {
    // activate all neighbors that are face+edge+vertex
    // connected to the current pixel. do not include the center pixel
    const unsigned int centerIndex = it->GetCenterNeighborhoodIndex();
    for (unsigned int d = 0; d < centerIndex * 2 + 1; ++d)
    {
      const typename TIterator::OffsetType offset = it->GetOffset(d);
      it->ActivateOffset(offset);
    }
    const typename TIterator::OffsetType offset_zeros{};
    it->DeactivateOffset(offset_zeros);
  }
  return it;
}
 
template <typename TIterator>
TIterator *
setConnectivityPrevious(TIterator * it, bool fullyConnected = false)
{
  // activate the "previous" neighbours
  it->ClearActiveList();
  if (!fullyConnected)
  {
    // only activate the neighbors that are face connected
    // to the current pixel. do not include the center pixel
    typename TIterator::OffsetType offset{};
    for (unsigned int d = 0; d < TIterator::Dimension; ++d)
    {
      offset[d] = -1;
      it->ActivateOffset(offset);
      offset[d] = 0;
    }
  }
  else
  {
    // activate all neighbors that are face+edge+vertex
    // connected to the current pixel. do not include the center pixel
    const unsigned int centerIndex = it->GetCenterNeighborhoodIndex();
    for (unsigned int d = 0; d < centerIndex; ++d)
    {
      const typename TIterator::OffsetType offset = it->GetOffset(d);
      it->ActivateOffset(offset);
    }
    const typename TIterator::OffsetType offset_zeros{};
    it->DeactivateOffset(offset_zeros);
  }
  return it;
}
 
template <typename TIterator>
TIterator *
setConnectivityLater(TIterator * it, bool fullyConnected = false)
{
  // activate the "later" neighbours
 
  it->ClearActiveList();
  if (!fullyConnected)
  {
    // only activate the neighbors that are face connected
    // to the current pixel. do not include the center pixel
    typename TIterator::OffsetType offset{};
    for (unsigned int d = 0; d < TIterator::Dimension; ++d)
    {
      offset[d] = 1;
      it->ActivateOffset(offset);
      offset[d] = 0;
    }
  }
  else
  {
    // activate all neighbors that are face+edge+vertex
    // connected to the current pixel. do not include the center pixel
    const unsigned int centerIndex = it->GetCenterNeighborhoodIndex();
    for (unsigned int d = centerIndex + 1; d < 2 * centerIndex + 1; ++d)
    {
      const typename TIterator::OffsetType offset = it->GetOffset(d);
      it->ActivateOffset(offset);
    }
    const typename TIterator::OffsetType offset_zeros{};
    it->DeactivateOffset(offset_zeros);
  }
  return it;
}
} // namespace itk
 
#endif