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/*=========================================================================
*
* Copyright UMC Utrecht and contributors
*
* 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
*
* http://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 itkExponentialLimiterFunction_h
#define itkExponentialLimiterFunction_h
#include "itkLimiterFunctionBase.h"
namespace itk
{
/**
* \class ExponentialLimiterFunction
* \brief A soft limiter
*
* If the input value exceeds the upper/lower threshold the output is
* diminished/increased, such that it never will exceed the UpperBound/LowerBound.
* It does this in a smooth manner, with an exponential function.
*
* \f[ L(f(x)) = (T-B) e^{(f-T)/(T-B)} + B, \f]
* where \f$B\f$ is the upper/lower bound and \f$T\f$ the upper/lower threshold
*
* \ingroup Functions
* \sa LimiterFunctionBase, HardLimiterFunction
*
*/
template <class TInput, unsigned int NDimension>
class ITK_TEMPLATE_EXPORT ExponentialLimiterFunction : public LimiterFunctionBase<TInput, NDimension>
{
public:
ITK_DISALLOW_COPY_AND_MOVE(ExponentialLimiterFunction);
/** Standard class typedefs. */
using Self = ExponentialLimiterFunction;
using Superclass = LimiterFunctionBase<TInput, NDimension>;
using Pointer = SmartPointer<Self>;
using ConstPointer = SmartPointer<const Self>;
/** Run-time type information (and related methods). */
itkTypeMacro(ExponentialLimiterFunction, LimiterFunctionBase);
/** Define the New() function, for creation via the ObjectFactory */
itkNewMacro(Self);
/** Superclass' static consts */
itkStaticConstMacro(Dimension, unsigned int, Superclass::Dimension);
/** Superclass' typedefs */
using typename Superclass::InputType;
using typename Superclass::OutputType;
using typename Superclass::DerivativeValueType;
using typename Superclass::DerivativeType;
/** Limit the input value */
OutputType
Evaluate(const InputType & input) const override;
/** Limit the input value and change the input function derivative accordingly */
OutputType
Evaluate(const InputType & input, DerivativeType & derivative) const override;
/** Initialize the limiter; calls the ComputeLimiterSettings() function */
void
Initialize() override;
protected:
ExponentialLimiterFunction();
~ExponentialLimiterFunction() override = default;
virtual void
ComputeLimiterSettings();
double m_UTminUB{};
double m_UTminUBinv{};
double m_LTminLB{};
double m_LTminLBinv{};
};
} // end namespace itk
#ifndef ITK_MANUAL_INSTANTIATION
# include "itkExponentialLimiterFunction.hxx"
#endif
#endif
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