itkImageHelper.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 itkImageHelper_h
#define itkImageHelper_h
 
#include "itkMacro.h" // For ITK_TEMPLATE_EXPORT.
 
namespace itk
{
// Forward reference because of circular dependencies
template <unsigned int VImageDimension>
class ITK_TEMPLATE_EXPORT ImageBase;
 
template <unsigned int VImageDimension, unsigned int VLoop>
class ImageHelper
{
public:
  using ImageType = ImageBase<VImageDimension>;
  using IndexType = typename ImageType::IndexType;
  using OffsetType = typename ImageType::OffsetType;
  using OffsetValueType = typename ImageType::OffsetValueType;
  using IndexValueType = typename ImageType::IndexValueType;
 
  static inline void
  ComputeIndex(const IndexType &                      bufferedRegionIndex,
               OffsetValueType                        offset,
               [[maybe_unused]] const OffsetValueType offsetTable[],
               IndexType &                            index)
  {
    static_assert(VLoop <= VImageDimension);
 
    if constexpr (VLoop > 1)
    {
      constexpr unsigned int loopIndex{ VLoop - 1 };
 
      index[loopIndex] = static_cast<IndexValueType>(offset / offsetTable[loopIndex]);
      offset -= (index[loopIndex] * offsetTable[loopIndex]);
      index[loopIndex] += bufferedRegionIndex[loopIndex];
      ImageHelper<VImageDimension, loopIndex>::ComputeIndex(bufferedRegionIndex, offset, offsetTable, index);
    }
    else
    {
      static_assert(VLoop == 1);
 
      // Do last
      index[0] = bufferedRegionIndex[0] + static_cast<IndexValueType>(offset);
    }
  }
 
  // ComputeOffset
  //
  static inline void
  ComputeOffset(const IndexType &                      bufferedRegionIndex,
                const IndexType &                      index,
                [[maybe_unused]] const OffsetValueType offsetTable[],
                OffsetValueType &                      offset)
  {
    static_assert(VLoop <= VImageDimension);
 
    if constexpr (VLoop > 1)
    {
      constexpr unsigned int loopIndex{ VLoop - 1 };
 
      offset += (index[loopIndex] - bufferedRegionIndex[loopIndex]) * offsetTable[loopIndex];
      ImageHelper<VImageDimension, loopIndex>::ComputeOffset(bufferedRegionIndex, index, offsetTable, offset);
    }
    else
    {
      static_assert(VLoop == 1);
 
      // Do last
      offset += index[0] - bufferedRegionIndex[0];
    }
  }
};
} // end namespace itk
 
#endif