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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 itkBSplineInterpolationWeightFunction_hxx
#define itkBSplineInterpolationWeightFunction_hxx
#include "itkBSplineKernelFunction.h"
#include "itkImage.h"
#include "itkMatrix.h"
#include "itkMath.h"
namespace itk
{
/** Compute weights for interpolation at continuous index position */
template <typename TCoordRep, unsigned int VSpaceDimension, unsigned int VSplineOrder>
auto
BSplineInterpolationWeightFunction<TCoordRep, VSpaceDimension, VSplineOrder>::Evaluate(
const ContinuousIndexType & index) const -> WeightsType
{
WeightsType weights;
IndexType startIndex;
this->Evaluate(index, weights, startIndex);
return weights;
}
/** Compute weights for interpolation at continuous index position */
template <typename TCoordRep, unsigned int VSpaceDimension, unsigned int VSplineOrder>
void
BSplineInterpolationWeightFunction<TCoordRep, VSpaceDimension, VSplineOrder>::Evaluate(
const ContinuousIndexType & index,
WeightsType & weights,
IndexType & startIndex) const
{
unsigned int j, k;
// Find the starting index of the support region
for (j = 0; j < SpaceDimension; ++j)
{
// Note that the expression passed to Math::Floor is adapted to work around
// a compiler bug which caused endless compilations (apparently), by
// Visual C++ 2015 Update 3, on 64-bit builds of Release configurations.
startIndex[j] = Math::Floor<IndexValueType>(index[j] + 0.5 - SplineOrder / 2.0);
}
// Compute the weights
Matrix<double, SpaceDimension, SplineOrder + 1> weights1D;
for (j = 0; j < SpaceDimension; ++j)
{
double x = index[j] - static_cast<double>(startIndex[j]);
for (k = 0; k <= SplineOrder; ++k)
{
weights1D[j][k] = BSplineKernelFunction<SplineOrder>::FastEvaluate(x);
x -= 1.0;
}
}
for (k = 0; k < Self::NumberOfWeights; ++k)
{
weights[k] = 1.0;
for (j = 0; j < SpaceDimension; ++j)
{
weights[k] *= weights1D[j][m_OffsetToIndexTable[k][j]];
}
}
}
} // end namespace itk
#endif
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