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/*=========================================================================
Program: Insight Segmentation & Registration Toolkit
Module: itkVectorLinearInterpolateNearestNeighborExtrapolateImageFunction.txx
Language: C++
Date: $Date$
Version: $Revision$
Copyright (c) Insight Software Consortium. All rights reserved.
See ITKCopyright.txt or http://www.itk.org/HTML/Copyright.htm for details.
This software is distributed WITHOUT ANY WARRANTY; without even
the implied warranty of MERCHANTABILITY or FITNESS FOR A PARTICULAR
PURPOSE. See the above copyright notices for more information.
=========================================================================*/
#ifndef __itkVectorLinearInterpolateNearestNeighborExtrapolateImageFunction_txx
#define __itkVectorLinearInterpolateNearestNeighborExtrapolateImageFunction_txx
#include "itkVectorLinearInterpolateNearestNeighborExtrapolateImageFunction.h"
#include "vnl/vnl_math.h"
namespace itk
{
/**
* Define the number of neighbors
*/
template<class TInputImage, class TCoordRep>
const unsigned long
VectorLinearInterpolateNearestNeighborExtrapolateImageFunction< TInputImage, TCoordRep >
::m_Neighbors = 1 << TInputImage::ImageDimension;
/**
* Constructor
*/
template<class TInputImage, class TCoordRep>
VectorLinearInterpolateNearestNeighborExtrapolateImageFunction< TInputImage, TCoordRep >
::VectorLinearInterpolateNearestNeighborExtrapolateImageFunction()
{
}
/**
* PrintSelf
*/
template<class TInputImage, class TCoordRep>
void
VectorLinearInterpolateNearestNeighborExtrapolateImageFunction< TInputImage, TCoordRep >
::PrintSelf(std::ostream& os, Indent indent) const
{
this->Superclass::PrintSelf(os,indent);
}
/**
* Evaluate at image index position
*/
template<class TInputImage, class TCoordRep>
typename VectorLinearInterpolateNearestNeighborExtrapolateImageFunction< TInputImage, TCoordRep >
::OutputType
VectorLinearInterpolateNearestNeighborExtrapolateImageFunction< TInputImage, TCoordRep >
::EvaluateAtContinuousIndex( const ContinuousIndexType& index) const
{
unsigned int dim; // index over dimension
/**
* Compute base index = closest index below point
* Compute distance from point to base index
*/
IndexType baseIndex;
IndexType neighIndex;
double distance[ImageDimension];
for( dim = 0; dim < ImageDimension; dim++ )
{
baseIndex[dim] = Math::Floor<IndexValueType>( index[dim] );
if( baseIndex[dim] >= this->m_StartIndex[dim] )
{
if( baseIndex[dim] < this->m_EndIndex[dim] )
{
distance[dim] = index[dim] - static_cast<double>( baseIndex[dim] );
}
else
{
baseIndex[dim] = this->m_EndIndex[dim];
distance[dim] = 0.0;
}
}
else
{
baseIndex[dim] = this->m_StartIndex[dim];
distance[dim] = 0.0;
}
}
/**
* Interpolated value is the weight some of each of the surrounding
* neighbors. The weight for each neighbour is the fraction overlap
* of the neighbor pixel with respect to a pixel centered on point.
*/
OutputType output;
output.Fill( 0.0 );
RealType totalOverlap = 0.0;
for( unsigned int counter = 0; counter < m_Neighbors; counter++ )
{
double overlap = 1.0; // fraction overlap
unsigned int upper = counter; // each bit indicates upper/lower neighbour
// get neighbor index and overlap fraction
for( dim = 0; dim < ImageDimension; dim++ )
{
if( upper & 1 )
{
neighIndex[dim] = baseIndex[dim] + 1;
overlap *= distance[dim];
}
else
{
neighIndex[dim] = baseIndex[dim];
overlap *= 1.0 - distance[dim];
}
upper >>= 1;
}
// get neighbor value only if overlap is not zero
if( overlap )
{
const PixelType input = this->GetInputImage()->GetPixel( neighIndex );
for(unsigned int k = 0; k < Dimension; k++ )
{
output[k] += overlap * static_cast<RealType>( input[k] );
}
totalOverlap += overlap;
}
if( totalOverlap == 1.0 )
{
// finished
break;
}
}
return ( output );
}
/**
* Evaluate at image index position
*/
template<class TInputImage, class TCoordRep>
typename VectorLinearInterpolateNearestNeighborExtrapolateImageFunction< TInputImage, TCoordRep >
::OutputType
VectorLinearInterpolateNearestNeighborExtrapolateImageFunction< TInputImage, TCoordRep >
::EvaluateAtIndex( const IndexType & index) const
{
// Find the index that is closest to the requested one
// but that lies within the image
IndexType insideIndex;
for( unsigned int dim = 0; dim < ImageDimension; dim++ )
{
if( index[dim] >= this->m_StartIndex[dim] )
{
if( index[dim] < this->m_EndIndex[dim] )
{
insideIndex[dim] = index[dim];
}
else
{
insideIndex[dim] = this->m_EndIndex[dim];
}
}
else
{
insideIndex[dim] = this->m_StartIndex[dim];
}
}
// Now call the superclass implementation of EvaluateAtIndex
// since we have ensured that the index lies in the image region
return this->Superclass::EvaluateAtIndex( insideIndex );
}
} // end namespace itk
#endif
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