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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 itkGaussianKernelFunction_h
#define itkGaussianKernelFunction_h
#include "itkKernelFunctionBase.h"
#include "itkMath.h"
#include <cmath>
namespace itk
{
/** \class GaussianKernelFunction
* \brief Gaussian kernel used for density estimation and nonparametric
* regression.
*
* This class encapsulates a Gaussian smoothing kernel for
* density estimation or nonparametric regression.
* See documentation for KernelFunctionBase for more details.
*
* \sa KernelFunctionBase
*
* \ingroup Functions
* \ingroup ITKCommon
*/
template <typename TRealValueType = double>
class ITK_TEMPLATE_EXPORT GaussianKernelFunction : public KernelFunctionBase<TRealValueType>
{
public:
ITK_DISALLOW_COPY_AND_MOVE(GaussianKernelFunction);
/** Standard class type aliases. */
using Self = GaussianKernelFunction;
using Superclass = KernelFunctionBase<TRealValueType>;
using Pointer = SmartPointer<Self>;
using typename Superclass::RealType;
/** Method for creation through the object factory. */
itkNewMacro(Self);
/** \see LightObject::GetNameOfClass() */
itkOverrideGetNameOfClassMacro(GaussianKernelFunction);
/** Evaluate the function. */
TRealValueType
Evaluate(const TRealValueType & u) const override
{
return (std::exp(TRealValueType{ -0.5 } * itk::Math::sqr(u)) * m_Factor);
}
protected:
GaussianKernelFunction()
: m_Factor(TRealValueType{ 1.0 } / std::sqrt(TRealValueType{ 2.0 * itk::Math::pi })){};
~GaussianKernelFunction() override = default;
void
PrintSelf(std::ostream & os, Indent indent) const override
{
Superclass::PrintSelf(os, indent);
}
private:
const TRealValueType m_Factor{};
};
} // end namespace itk
#endif
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