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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 itkRectangularImageNeighborhoodShape_h
#define itkRectangularImageNeighborhoodShape_h
#include <algorithm> // For transform.
#include <cassert>
#include "itkOffset.h"
#include "itkSize.h"
namespace itk
{
/**
* \class RectangularImageNeighborhoodShape
* Rectangular (or hyperrectangular) image-neighborhood shape.
* Eases creating a sequence of offsets for ShapedImageNeighborhoodRange.
* Can also be used for ShapedNeighborhoodIterator.
*
* The following example creates a 3 x 5 rectangular neighborhood around
* pixel location [10, 20], and generates the offsets for a neighborhood range:
\code
const Index<> location = { 10, 20 };
const Size<> radius = { { 1, 2 } };
const RectangularImageNeighborhoodShape<2> shape{ radius };
const std::vector<Offset<>> offsets = GenerateImageNeighborhoodOffsets(shape);
ShapedImageNeighborhoodRange<ImageType> neighborhoodRange{ *image, location, offsets };
\endcode
*
* \see ShapedNeighborhoodIterator
* \see ShapedImageNeighborhoodRange
* \ingroup ImageIterators
* \ingroup ITKCommon
*/
template <unsigned int VImageDimension>
class RectangularImageNeighborhoodShape
{
public:
static constexpr unsigned int ImageDimension = VImageDimension;
/** Constructs a hyperrectangular shape whose size is specified by the radius */
constexpr explicit RectangularImageNeighborhoodShape(const Size<ImageDimension> & radius) noexcept
: m_Radius(radius)
, m_NumberOfOffsets(CalculateNumberOfOffsets(ImageDimension))
{}
/** Returns the number of offsets needed to represent this shape. */
constexpr size_t
GetNumberOfOffsets() const noexcept
{
return m_NumberOfOffsets;
}
/** Fills the specified buffer with the offsets for a neighborhood of this shape. */
void
FillOffsets(Offset<ImageDimension> * const offsets) const noexcept
{
if (m_NumberOfOffsets > 0)
{
assert(offsets != nullptr);
Offset<ImageDimension> offset;
std::transform(m_Radius.begin(), m_Radius.end(), offset.begin(), [](const SizeValueType radiusValue) {
return -static_cast<OffsetValueType>(radiusValue);
});
for (size_t i = 0; i < m_NumberOfOffsets; ++i)
{
offsets[i] = offset;
for (unsigned int dimensionIndex = 0; dimensionIndex < ImageDimension; ++dimensionIndex)
{
OffsetValueType & offsetValue = offset[dimensionIndex];
++offsetValue;
if (offsetValue <= static_cast<OffsetValueType>(m_Radius[dimensionIndex]))
{
break;
}
offsetValue = -static_cast<OffsetValueType>(m_Radius[dimensionIndex]);
}
}
}
}
private:
// The radius of the neighborhood along each direction.
Size<ImageDimension> m_Radius;
// The number of offsets needed to represent this shape.
size_t m_NumberOfOffsets;
// Private helper function to calculate the number of Offsets by a recursive
// function call. Recursion is necessary for C++11 constexpr.
constexpr size_t
CalculateNumberOfOffsets(const unsigned int dimension) const noexcept
{
return (dimension == 0)
? 1
: (2 * m_Radius.m_InternalArray[dimension - 1] + 1) * CalculateNumberOfOffsets(dimension - 1);
}
};
} // namespace itk
#endif
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