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/*========================================================================= |
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Program: Insight Segmentation & Registration Toolkit |
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Module: $RCSfile: itkLinearInterpolateImageFunction.txx.html,v $ |
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Language: C++ |
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Date: $Date: 2006/01/17 19:15:41 $ |
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Version: $Revision: 1.4 $ |
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Copyright (c) Insight Software Consortium. All rights reserved. |
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See ITKCopyright.txt or http://www.itk.org/HTML/Copyright.htm for details. |
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This software is distributed WITHOUT ANY WARRANTY; without even |
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the implied warranty of MERCHANTABILITY or FITNESS FOR A PARTICULAR |
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PURPOSE. See the above copyright notices for more information. |
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=========================================================================*/ |
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DEF |
#ifndef _itkLinearInterpolateImageFunction_txx |
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DEF |
#define _itkLinearInterpolateImageFunction_txx |
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#include "itkLinearInterpolateImageFunction.h" |
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#include "vnl/vnl_math.h" |
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namespace itk |
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{ |
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/** |
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* Define the number of neighbors |
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*/ |
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template<class TInputImage, class TCoordRep> |
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const unsigned long |
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LinearInterpolateImageFunction< TInputImage, TCoordRep > |
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::m_Neighbors = 1 << TInputImage::ImageDimension; |
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/** |
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* Constructor |
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*/ |
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template<class TInputImage, class TCoordRep> |
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LinearInterpolateImageFunction< TInputImage, TCoordRep > |
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::LinearInterpolateImageFunction() |
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{ |
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} |
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/** |
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* PrintSelf |
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*/ |
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template<class TInputImage, class TCoordRep> |
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void |
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LinearInterpolateImageFunction< TInputImage, TCoordRep > |
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::PrintSelf(std::ostream& os, Indent indent) const |
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{ |
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this->Superclass::PrintSelf(os,indent); |
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} |
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/** |
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* Evaluate at image index position |
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*/ |
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template<class TInputImage, class TCoordRep> |
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typename LinearInterpolateImageFunction< TInputImage, TCoordRep > |
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::OutputType |
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LinearInterpolateImageFunction< TInputImage, TCoordRep > |
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::EvaluateAtContinuousIndex( |
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const ContinuousIndexType& index) const |
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{ |
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unsigned int dim; // index over dimension |
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/** |
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* Compute base index = closet index below point |
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* Compute distance from point to base index |
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*/ |
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signed long baseIndex[ImageDimension]; |
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double distance[ImageDimension]; |
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long tIndex; |
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for( dim = 0; dim < ImageDimension; dim++ ) |
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{ |
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// The following "if" block is equivalent to the following line without |
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// having to call floor. |
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// baseIndex[dim] = (long) floor( index[dim] ); |
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if (index[dim] >= 0.0) |
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{ |
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baseIndex[dim] = (long) index[dim]; |
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} |
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else |
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{ |
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tIndex = (long) index[dim]; |
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if (double(tIndex) != index[dim]) |
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{ |
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tIndex--; |
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} |
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baseIndex[dim] = tIndex; |
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} |
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distance[dim] = index[dim] - double( baseIndex[dim] ); |
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} |
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/** |
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* Interpolated value is the weighted sum of each of the surrounding |
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* neighbors. The weight for each neighbor is the fraction overlap |
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* of the neighbor pixel with respect to a pixel centered on point. |
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*/ |
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RealType value = NumericTraits<RealType>::Zero; |
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RealType totalOverlap = NumericTraits<RealType>::Zero; |
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for( unsigned int counter = 0; counter < m_Neighbors; counter++ ) |
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{ |
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double overlap = 1.0; // fraction overlap |
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unsigned int upper = counter; // each bit indicates upper/lower neighbour |
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IndexType neighIndex; |
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// get neighbor index and overlap fraction |
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for( dim = 0; dim < ImageDimension; dim++ ) |
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{ |
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if ( upper & 1 ) |
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{ |
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neighIndex[dim] = baseIndex[dim] + 1; |
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overlap *= distance[dim]; |
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} |
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else |
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{ |
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neighIndex[dim] = baseIndex[dim]; |
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overlap *= 1.0 - distance[dim]; |
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} |
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upper >>= 1; |
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} |
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// get neighbor value only if overlap is not zero |
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if( overlap ) |
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{ |
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value += overlap * static_cast<RealType>( this->GetInputImage()->GetPixel( neighIndex ) ); |
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totalOverlap += overlap; |
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} |
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if( totalOverlap == 1.0 ) |
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{ |
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// finished |
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break; |
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} |
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} |
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return ( static_cast<OutputType>( value ) ); |
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} |
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} // namespace itk |
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#endif |
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