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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 itkCovarianceImageFunction_hxx
#define itkCovarianceImageFunction_hxx
#include "itkMatrix.h"
#include "itkConstNeighborhoodIterator.h"
namespace itk
{
template <typename TInputImage, typename TCoordRep>
CovarianceImageFunction<TInputImage, TCoordRep>::CovarianceImageFunction()
= default;
template <typename TInputImage, typename TCoordRep>
auto
CovarianceImageFunction<TInputImage, TCoordRep>::EvaluateAtIndex(const IndexType & index) const -> RealType
{
using PixelType = typename TInputImage::PixelType;
using PixelComponentType = typename PixelType::ValueType;
using PixelComponentRealType = typename NumericTraits<PixelComponentType>::RealType;
if (!this->GetInputImage())
{
itkExceptionMacro("No image connected to CovarianceImageFunction");
}
const unsigned int VectorDimension = this->GetInputImage()->GetNumberOfComponentsPerPixel();
RealType covariance(VectorDimension, VectorDimension);
if (!this->IsInsideBuffer(index))
{
covariance.fill(NumericTraits<PixelComponentRealType>::max());
return covariance;
}
covariance.fill(PixelComponentRealType{});
using MeanVectorType = vnl_vector<PixelComponentRealType>;
MeanVectorType mean(VectorDimension);
mean.fill(PixelComponentRealType{});
// 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 PixelType pixel = it.GetPixel(i);
for (unsigned int dimx = 0; dimx < VectorDimension; ++dimx)
{
mean[dimx] += pixel[dimx];
for (unsigned int dimy = 0; dimy < VectorDimension; ++dimy)
{
covariance[dimx][dimy] +=
static_cast<PixelComponentRealType>(pixel[dimx]) * static_cast<PixelComponentRealType>(pixel[dimy]);
}
}
}
const auto rsize = static_cast<PixelComponentRealType>(size);
mean /= rsize;
for (unsigned int dimx = 0; dimx < VectorDimension; ++dimx)
{
for (unsigned int dimy = 0; dimy < VectorDimension; ++dimy)
{
covariance[dimx][dimy] /= rsize;
covariance[dimx][dimy] -= mean[dimx] * mean[dimy];
}
}
return (covariance);
}
template <typename TInputImage, typename TCoordRep>
void
CovarianceImageFunction<TInputImage, TCoordRep>::PrintSelf(std::ostream & os, Indent indent) const
{
Superclass::PrintSelf(os, indent);
os << indent << "NeighborhoodRadius: " << m_NeighborhoodRadius << std::endl;
}
} // end namespace itk
#endif
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