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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 itkHessian3DToVesselnessMeasureImageFilter_hxx
#define itkHessian3DToVesselnessMeasureImageFilter_hxx
#include "itkImageRegionIterator.h"
#include "itkMath.h"
namespace itk
{
template <typename TPixel>
Hessian3DToVesselnessMeasureImageFilter<TPixel>::Hessian3DToVesselnessMeasureImageFilter()
{
m_Alpha1 = 0.5;
m_Alpha2 = 2.0;
// Hessian( Image ) = Jacobian( Gradient ( Image ) ) is symmetric
m_SymmetricEigenValueFilter = EigenAnalysisFilterType::New();
m_SymmetricEigenValueFilter->OrderEigenValuesBy(EigenValueOrderEnum::OrderByValue);
}
template <typename TPixel>
void
Hessian3DToVesselnessMeasureImageFilter<TPixel>::GenerateData()
{
itkDebugMacro("Hessian3DToVesselnessMeasureImageFilter generating data ");
m_SymmetricEigenValueFilter->SetInput(this->GetInput());
typename OutputImageType::Pointer output = this->GetOutput();
using EigenValueOutputImageType = typename EigenAnalysisFilterType::OutputImageType;
m_SymmetricEigenValueFilter->Update();
const typename EigenValueOutputImageType::ConstPointer eigenImage = m_SymmetricEigenValueFilter->GetOutput();
// walk the region of eigen values and get the vesselness measure
EigenValueArrayType eigenValue;
ImageRegionConstIterator<EigenValueOutputImageType> it;
it = ImageRegionConstIterator<EigenValueOutputImageType>(eigenImage, eigenImage->GetRequestedRegion());
ImageRegionIterator<OutputImageType> oit;
this->AllocateOutputs();
oit = ImageRegionIterator<OutputImageType>(output, output->GetRequestedRegion());
while (!it.IsAtEnd())
{
// Get the eigen value
eigenValue = it.Get();
// normalizeValue <= 0 for bright line structures
double normalizeValue = std::min(-1.0 * eigenValue[1], -1.0 * eigenValue[0]);
// Similarity measure to a line structure
if (normalizeValue > 0)
{
double lineMeasure;
if (eigenValue[2] <= 0)
{
lineMeasure = std::exp(-0.5 * itk::Math::sqr(eigenValue[2] / (m_Alpha1 * normalizeValue)));
}
else
{
lineMeasure = std::exp(-0.5 * itk::Math::sqr(eigenValue[2] / (m_Alpha2 * normalizeValue)));
}
lineMeasure *= normalizeValue;
oit.Set(static_cast<OutputPixelType>(lineMeasure));
}
else
{
oit.Set(OutputPixelType{});
}
++it;
++oit;
}
}
template <typename TPixel>
void
Hessian3DToVesselnessMeasureImageFilter<TPixel>::PrintSelf(std::ostream & os, Indent indent) const
{
Superclass::PrintSelf(os, indent);
os << indent << "Alpha1: " << m_Alpha1 << std::endl;
os << indent << "Alpha2: " << m_Alpha2 << std::endl;
}
} // end namespace itk
#endif
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