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/*=========================================================================
*
* Copyright Insight Software Consortium
*
* 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 itkCovarianceImageFunction_hxx
#define itkCovarianceImageFunction_hxx
#include "itkCovarianceImageFunction.h"
#include "itkMatrix.h"
#include "itkConstNeighborhoodIterator.h"
namespace itk
{
template< typename TInputImage, typename TCoordRep >
CovarianceImageFunction< TInputImage, TCoordRep >
::CovarianceImageFunction() :
m_NeighborhoodRadius( 1 )
{
}
template< typename TInputImage, typename TCoordRep >
typename CovarianceImageFunction< TInputImage, TCoordRep >
::RealType
CovarianceImageFunction< TInputImage, TCoordRep >
::EvaluateAtIndex(const IndexType & index) const
{
typedef typename TInputImage::PixelType PixelType;
typedef typename PixelType::ValueType PixelComponentType;
typedef typename NumericTraits< PixelComponentType >::RealType PixelComponentRealType;
if ( !this->GetInputImage() )
{
itkExceptionMacro(<< "No image connected to CovarianceImageFunction");
}
const unsigned int VectorDimension = this->GetInputImage()->GetNumberOfComponentsPerPixel();
RealType covariance = RealType(VectorDimension, VectorDimension);
if ( !this->IsInsideBuffer(index) )
{
covariance.fill( NumericTraits< PixelComponentRealType >::max() );
return covariance;
}
covariance.fill(NumericTraits< PixelComponentRealType >::ZeroValue());
typedef vnl_vector< PixelComponentRealType > MeanVectorType;
MeanVectorType mean = MeanVectorType(VectorDimension);
mean.fill(NumericTraits< PixelComponentRealType >::ZeroValue());
// 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 PixelComponentRealType 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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