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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_h
#define itkLaplacianOperator_h
#include "itkNeighborhoodOperator.h"
namespace itk
{
/**
* \class LaplacianOperator
* \brief A NeighborhoodOperator for use in calculating the Laplacian at a pixel.
*
* A NeighborhoodOperator for use in calculating the Laplacian at a pixel.
* The LaplacianOperator's coefficients are a tightest-fitting convolution
* kernel.
*
* For example, the simplest Laplacian Operator for 2D has the form:
\code
0 1 0
1 -4 1
0 1 0
\endcode
*
* \par
* The LaplacianOperator is a non-directional NeighborhoodOperator that
* should be applied to a Neighborhood or NeighborhoodIterator using an inner
* product method (itkNeighborhoodInnerProduct). To initialize the operator, you
* need call CreateOperator() before using it.
*
* \par
* By default the operator will be created for an isotropic image, but you can
* modify the operator to handle different pixel spacings by calling
* SetDerivativeScalings. The argument to SetDerivativeScalings is an array
* of doubles that is of length VDimension (the dimensionality of the image).
* Make sure to use 1/pixel_spacing to properly scale derivatives.
*
* \note LaplacianOperator does not have any user-declared "special member function"
* for copy, move, or destruction, following the C++ Rule of Zero: the compiler will
* generate them if necessary.
*
* \sa NeighborhoodOperator
* \sa Neighborhood
* \ingroup Operators
* \ingroup ITKCommon
*
* \sphinx
* \sphinxexample{Core/Common/CreateLaplacianKernel,Create Laplacian Kernel}
* \endsphinx
*/
template <typename TPixel, unsigned int VDimension = 2, typename TAllocator = NeighborhoodAllocator<TPixel>>
class ITK_TEMPLATE_EXPORT LaplacianOperator : public NeighborhoodOperator<TPixel, VDimension, TAllocator>
{
public:
/** Standard class type aliases. */
using Self = LaplacianOperator;
using Superclass = NeighborhoodOperator<TPixel, VDimension, TAllocator>;
/** \see LightObject::GetNameOfClass() */
itkOverrideGetNameOfClassMacro(LaplacianOperator);
using typename Superclass::SizeType;
LaplacianOperator()
{
for (unsigned int i = 0; i < VDimension; ++i)
{
m_DerivativeScalings[i] = 1.0;
}
}
/** Create the operator. */
void
CreateOperator();
void
PrintSelf(std::ostream & os, Indent indent) const override
{
Superclass::PrintSelf(os, indent);
os << indent << "DerivativeScalings: " << m_DerivativeScalings << std::endl;
}
/** Sets the weights that are applied to the derivative in each axial
* direction when the kernel is computed. These weights are all 1.0 by
* default. This method must be called BEFORE CreateOperator */
void
SetDerivativeScalings(const double * s);
itkGetConstMacro(DerivativeScalings, const double *);
protected:
/** Type alias support for coefficient vector type.*/
using typename Superclass::CoefficientVector;
/** Calculates operator coefficients. */
CoefficientVector
GenerateCoefficients() override;
/** Arranges coefficients spatially in the memory buffer, default
* function was NOT used. */
void
Fill(const CoefficientVector &) override;
private:
/** Weights applied to derivatives in each axial direction */
double m_DerivativeScalings[VDimension]{};
};
} // namespace itk
#ifndef ITK_MANUAL_INSTANTIATION
# include "itkLaplacianOperator.hxx"
#endif
#endif
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