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/*=========================================================================
Program: Insight Segmentation & Registration Toolkit
Module: $RCSfile: itkVectorLinearInterpolateImageFunction.txx,v $
Language: C++
Date: $Date: 2006-03-19 04:36:59 $
Version: $Revision: 1.15 $
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 __itkVectorLinearInterpolateImageFunction_txx
#define __itkVectorLinearInterpolateImageFunction_txx
#include "itkVectorLinearInterpolateImageFunction.h"
#include "vnl/vnl_math.h"
namespace itk
{
/**
* Define the number of neighbors
*/
template<class TInputImage, class TCoordRep>
const unsigned long
VectorLinearInterpolateImageFunction< TInputImage, TCoordRep >
::m_Neighbors = 1 << TInputImage::ImageDimension;
/**
* Constructor
*/
template<class TInputImage, class TCoordRep>
VectorLinearInterpolateImageFunction< TInputImage, TCoordRep >
::VectorLinearInterpolateImageFunction()
{
}
/**
* PrintSelf
*/
template<class TInputImage, class TCoordRep>
void
VectorLinearInterpolateImageFunction< 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 VectorLinearInterpolateImageFunction< TInputImage, TCoordRep >
::OutputType
VectorLinearInterpolateImageFunction< TInputImage, TCoordRep >
::EvaluateAtContinuousIndex(
const ContinuousIndexType& index) const
{
unsigned int dim; // index over dimension
/**
* Compute base index = closet index below point
* Compute distance from point to base index
*/
signed long baseIndex[ImageDimension];
double distance[ImageDimension];
for( dim = 0; dim < ImageDimension; dim++ )
{
baseIndex[dim] = (long) vcl_floor(index[dim] );
distance[dim] = index[dim] - double( baseIndex[dim] );
}
/**
* 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
IndexType neighIndex;
// 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 );
}
} // end namespace itk
#endif
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