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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 itkLaplacianOperator_hxx
#define itkLaplacianOperator_hxx
namespace itk
{
template <typename TPixel, unsigned int VDimension, typename TAllocator>
void
LaplacianOperator<TPixel, VDimension, TAllocator>::SetDerivativeScalings(const double * s)
{
for (unsigned int i = 0; i < VDimension; ++i)
{
m_DerivativeScalings[i] = s[i];
}
}
// Create the operator
template <typename TPixel, unsigned int VDimension, typename TAllocator>
void
LaplacianOperator<TPixel, VDimension, TAllocator>::CreateOperator()
{
CoefficientVector coefficients;
coefficients = this->GenerateCoefficients();
this->Fill(coefficients);
}
// This function fills the coefficients into the corresponding neighborhood.
template <typename TPixel, unsigned int VDimension, typename TAllocator>
void
LaplacianOperator<TPixel, VDimension, TAllocator>::Fill(const CoefficientVector & coeff)
{
typename Superclass::CoefficientVector::const_iterator it;
const std::slice temp_slice(0, coeff.size(), 1);
typename Self::SliceIteratorType data(this, temp_slice);
it = coeff.begin();
// Copy the coefficients into the neighborhood
for (data = data.Begin(); data < data.End(); ++data, ++it)
{
*data = *it;
}
}
template <typename TPixel, unsigned int VDimension, typename TAllocator>
auto
LaplacianOperator<TPixel, VDimension, TAllocator>::GenerateCoefficients() -> CoefficientVector
{
unsigned int i, w;
// Here we set the radius to 1's, here the
// operator is 3x3 for 2D, 3x3x3 for 3D.
SizeType r;
r.Fill(1);
this->SetRadius(r);
// Create a vector of the correct size to hold the coefficients.
w = this->Size();
CoefficientVector coeffP(w);
// Set the coefficients
double sum = 0.0;
for (i = 0; i < 2 * VDimension; i += 2)
{
OffsetValueType stride = this->GetStride(i / 2);
const double hsq = m_DerivativeScalings[i / 2] * m_DerivativeScalings[i / 2];
coeffP[w / 2 - stride] = coeffP[w / 2 + stride] = hsq;
sum += 2.0 * hsq;
}
coeffP[w / 2] = -sum;
return coeffP;
}
} // namespace itk
#endif
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