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/*=========================================================================
Program: Insight Segmentation & Registration Toolkit
Module: $RCSfile: itkBSplineInterpolationWeightFunction.txx,v $
Language: C++
Date: $Date: 2008-03-21 00:47:43 $
Version: $Revision: 1.14 $
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 __itkBSplineInterpolationWeightFunction_txx
#define __itkBSplineInterpolationWeightFunction_txx
#include "itkBSplineInterpolationWeightFunction.h"
#include "itkImage.h"
#include "itkMatrix.h"
#include "itkImageRegionConstIteratorWithIndex.h"
// anonymous namespace
namespace
{
//--------------------------------------------------------------------------
// The 'floor' function on x86 and mips is many times slower than these
// and is used a lot in this code, optimize for different CPU architectures
inline int BSplineFloor(double x)
{
#if defined mips || defined sparc || defined __ppc__
return (int)((unsigned int)(x + 2147483648.0) - 2147483648U);
#elif defined i386 || defined _M_IX86
union { unsigned int hilo[2]; double d; } u;
u.d = x + 103079215104.0;
return (int)((u.hilo[1]<<16)|(u.hilo[0]>>16));
#else
return int(floor(x));
#endif
}
}
namespace itk
{
/** Constructor */
template <class TCoordRep, unsigned int VSpaceDimension,
unsigned int VSplineOrder>
BSplineInterpolationWeightFunction<TCoordRep, VSpaceDimension, VSplineOrder>
::BSplineInterpolationWeightFunction()
{
// Initialize the number of weights;
m_NumberOfWeights =
static_cast<unsigned long>( vcl_pow(static_cast<double>(SplineOrder + 1),
static_cast<double>(SpaceDimension) ) );
// Initialize support region is a hypercube of length SplineOrder + 1
m_SupportSize.Fill( SplineOrder + 1 );
// Initialize offset to index lookup table
m_OffsetToIndexTable.set_size( m_NumberOfWeights, SpaceDimension );
typedef Image<char,SpaceDimension> CharImageType;
typename CharImageType::Pointer tempImage = CharImageType::New();
tempImage->SetRegions( m_SupportSize );
tempImage->Allocate();
tempImage->FillBuffer( 0 );
typedef ImageRegionConstIteratorWithIndex<CharImageType> IteratorType;
IteratorType iterator( tempImage, tempImage->GetBufferedRegion() );
unsigned long counter = 0;
while ( !iterator.IsAtEnd() )
{
for(unsigned int j = 0; j < SpaceDimension; j++ )
{
m_OffsetToIndexTable[counter][j] = iterator.GetIndex()[j];
}
++counter;
++iterator;
}
// Initialize the interpolation kernel
m_Kernel = KernelType::New();
}
/**
* Standard "PrintSelf" method
*/
template <class TCoordRep, unsigned int VSpaceDimension,
unsigned int VSplineOrder>
void
BSplineInterpolationWeightFunction<TCoordRep, VSpaceDimension, VSplineOrder>
::PrintSelf(
std::ostream& os,
Indent indent) const
{
Superclass::PrintSelf( os, indent );
os << indent << "NumberOfWeights: " << m_NumberOfWeights << std::endl;
os << indent << "SupportSize: " << m_SupportSize << std::endl;
}
/** Compute weights for interpolation at continous index position */
template <class TCoordRep, unsigned int VSpaceDimension,
unsigned int VSplineOrder>
typename BSplineInterpolationWeightFunction<TCoordRep, VSpaceDimension,
VSplineOrder>
::WeightsType
BSplineInterpolationWeightFunction<TCoordRep, VSpaceDimension, VSplineOrder>
::Evaluate(
const ContinuousIndexType& index ) const
{
WeightsType weights( m_NumberOfWeights );
IndexType startIndex;
this->Evaluate( index, weights, startIndex );
return weights;
}
/** Compute weights for interpolation at continous index position */
template <class TCoordRep, unsigned int VSpaceDimension,
unsigned int VSplineOrder>
void BSplineInterpolationWeightFunction<TCoordRep, VSpaceDimension,
VSplineOrder>
::Evaluate(
const ContinuousIndexType & index,
WeightsType & weights,
IndexType & startIndex ) const
{
unsigned int j, k;
// Find the starting index of the support region
for ( j = 0; j < SpaceDimension; j++ )
{
startIndex[j] = static_cast<typename IndexType::IndexValueType>(
BSplineFloor( index[j] - static_cast<double>( SplineOrder - 1 ) / 2.0 ) );
}
// Compute the weights
Matrix<double,SpaceDimension,SplineOrder + 1> weights1D;
for ( j = 0; j < SpaceDimension; j++ )
{
double x = index[j] - static_cast<double>( startIndex[j] );
for( k = 0; k <= SplineOrder; k++ )
{
weights1D[j][k] = m_Kernel->Evaluate( x );
x -= 1.0;
}
}
for ( k = 0; k < m_NumberOfWeights; k++ )
{
weights[k] = 1.0;
for ( j = 0; j < SpaceDimension; j++ )
{
weights[k] *= weights1D[j][ m_OffsetToIndexTable[k][j] ];
}
}
}
} // end namespace itk
#endif
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