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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 itkVarianceImageFunction_hxx
#define itkVarianceImageFunction_hxx
#include "itkConstNeighborhoodIterator.h"
namespace itk
{
template <typename TInputImage, typename TCoordRep>
VarianceImageFunction<TInputImage, TCoordRep>::VarianceImageFunction()
{
m_NeighborhoodRadius = 1;
}
template <typename TInputImage, typename TCoordRep>
void
VarianceImageFunction<TInputImage, TCoordRep>::PrintSelf(std::ostream & os, Indent indent) const
{
this->Superclass::PrintSelf(os, indent);
os << indent << "NeighborhoodRadius: " << m_NeighborhoodRadius << std::endl;
}
template <typename TInputImage, typename TCoordRep>
auto
VarianceImageFunction<TInputImage, TCoordRep>::EvaluateAtIndex(const IndexType & index) const -> RealType
{
RealType sum;
RealType sumOfSquares;
RealType var;
sum = RealType{};
sumOfSquares = RealType{};
if (!this->GetInputImage())
{
return (NumericTraits<RealType>::max());
}
if (!this->IsInsideBuffer(index))
{
return (NumericTraits<RealType>::max());
}
// Create an N-d neighborhood kernel, using a zeroflux boundary condition
typename InputImageType::SizeType kernelSize;
kernelSize.Fill(m_NeighborhoodRadius);
ConstNeighborhoodIterator<InputImageType> it(
kernelSize, this->GetInputImage(), this->GetInputImage()->GetBufferedRegion());
// Set the iterator at the desired location
it.SetLocation(index);
// Walk the neighborhood
const unsigned int size = it.Size();
for (unsigned int i = 0; i < size; ++i)
{
const auto value = static_cast<RealType>(it.GetPixel(i));
sum += value;
sumOfSquares += value * value;
}
const auto num = static_cast<double>(size);
var = (sumOfSquares - (sum * sum / num)) / (num - 1.0);
return (var);
}
} // end namespace itk
#endif
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