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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 itkNearestNeighborExtrapolateImageFunction_h
#define itkNearestNeighborExtrapolateImageFunction_h
#include "itkExtrapolateImageFunction.h"
#include <algorithm> // For clamp.
namespace itk
{
/**
* \class NearestNeighborExtrapolateImageFunction
* \brief Nearest neighbor extrapolation of a scalar image.
*
* NearestNeighborExtrapolateImageFunction extrapolate image intensity at
* a specified point, continuous index or index by copying the intensity
* of the nearest neighbor within the image buffer.
*
* This class is templated
* over the input image type and the coordinate representation type
* (e.g. float or double).
*
* \ingroup ImageFunctions
* \ingroup ITKImageFunction
*/
template <typename TInputImage, typename TCoordRep = float>
class ITK_TEMPLATE_EXPORT NearestNeighborExtrapolateImageFunction
: public ExtrapolateImageFunction<TInputImage, TCoordRep>
{
public:
ITK_DISALLOW_COPY_AND_MOVE(NearestNeighborExtrapolateImageFunction);
/** Standard class type aliases. */
using Self = NearestNeighborExtrapolateImageFunction;
using Superclass = ExtrapolateImageFunction<TInputImage, TCoordRep>;
using Pointer = SmartPointer<Self>;
using ConstPointer = SmartPointer<const Self>;
/** \see LightObject::GetNameOfClass() */
itkOverrideGetNameOfClassMacro(NearestNeighborExtrapolateImageFunction);
/** Method for creation through the object factory. */
itkNewMacro(Self);
/** OutputType type alias support */
using typename Superclass::OutputType;
/** InputImageType type alias support */
using typename Superclass::InputImageType;
/** Dimension underlying input image. */
static constexpr unsigned int ImageDimension = Superclass::ImageDimension;
/** Index type alias support */
using typename Superclass::IndexType;
using IndexValueType = typename IndexType::IndexValueType;
/** ContinuousIndex type alias support */
using typename Superclass::ContinuousIndexType;
/** Evaluate the function at a ContinuousIndex position
*
* Returns the extrapolated image intensity at a
* specified position by returning the intensity of the
* nearest neighbor within the image buffer.
*
*/
OutputType
EvaluateAtContinuousIndex(const ContinuousIndexType & index) const override
{
IndexType nindex;
const IndexType startIndex = this->GetStartIndex();
const IndexType endIndex = this->GetEndIndex();
for (unsigned int j = 0; j < ImageDimension; ++j)
{
nindex[j] = std::clamp(Math::RoundHalfIntegerUp<IndexValueType>(index[j]), startIndex[j], endIndex[j]);
}
return static_cast<OutputType>(this->GetInputImage()->GetPixel(nindex));
}
/** Evaluate the function at a ContinuousIndex position
*
* Returns the extrapolated image intensity at a
* specified position by returning the intensity of the
* nearest neighbor within the image buffer.
*
*/
OutputType
EvaluateAtIndex(const IndexType & index) const override
{
IndexType nindex;
const IndexType startIndex = this->GetStartIndex();
const IndexType endIndex = this->GetEndIndex();
for (unsigned int j = 0; j < ImageDimension; ++j)
{
nindex[j] = std::clamp(index[j], startIndex[j], endIndex[j]);
}
return static_cast<OutputType>(this->GetInputImage()->GetPixel(nindex));
}
protected:
NearestNeighborExtrapolateImageFunction() = default;
~NearestNeighborExtrapolateImageFunction() override = default;
void
PrintSelf(std::ostream & os, Indent indent) const override
{
Superclass::PrintSelf(os, indent);
}
};
} // end namespace itk
#endif
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