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/*========================================================================= |
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Program: Insight Segmentation & Registration Toolkit |
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Module: $RCSfile: itkVectorNearestNeighborInterpolateImageFunction.txx.html,v $ |
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Language: C++ |
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Date: $Date: 2006/01/17 19:15:49 $ |
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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 _itkVectorNearestNeighborInterpolateImageFunction_txx |
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DEF |
#define _itkVectorNearestNeighborInterpolateImageFunction_txx |
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#include "itkVectorNearestNeighborInterpolateImageFunction.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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VectorNearestNeighborInterpolateImageFunction< 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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VectorNearestNeighborInterpolateImageFunction< TInputImage, TCoordRep > |
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::VectorNearestNeighborInterpolateImageFunction() |
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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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VectorNearestNeighborInterpolateImageFunction< 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, no bounds checking.... |
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* use IsInsideBuffer() if needed |
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*/ |
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/** |
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* The nearest neighbour is assumed to be the pixel that has the largest |
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* overlap with the pixel that is centered on the indicated point (defined |
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* by ContinuousIndexType& index. |
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* |
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* We also achieve speedup by noting that if overlap is > 1/2 it |
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* is the nearest neighbour and if < 1/m_Neighbors, it isn't. |
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* If all overlaps are the same, we choose the last neighbour. |
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*/ |
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template<class TInputImage, class TCoordRep> |
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typename VectorNearestNeighborInterpolateImageFunction< TInputImage, TCoordRep > |
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::OutputType |
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VectorNearestNeighborInterpolateImageFunction< 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 = closest 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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for( dim = 0; dim < ImageDimension; dim++ ) |
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{ |
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baseIndex[dim] = (long) floor( index[dim] ); |
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distance[dim] = index[dim] - double( baseIndex[dim] ); |
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} |
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OutputType output; |
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output.Fill( 0.0 ); |
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double uniformOverlap = (1/(static_cast <double> (m_Neighbors))); |
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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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double currentMaxOverlap = 0.0; // max overlap until now |
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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 greater than previous ones |
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if((overlap > uniformOverlap) && (overlap > currentMaxOverlap) ) |
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{ |
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const PixelType input = this->GetInputImage()->GetPixel( neighIndex ); |
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for(unsigned int k = 0; k < Dimension; k++ ) |
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{ |
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output[k] = static_cast<RealType>( input[k] ); |
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} |
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currentMaxOverlap = overlap; |
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} |
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if( currentMaxOverlap >= 0.5 ) |
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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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* If all overlaps are a the same, we adopt a uniform policy of choosing |
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* the last neighbor. Just a convention.. |
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*/ |
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if( (counter == (m_Neighbors-1)) && (currentMaxOverlap == uniformOverlap) ) |
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{ |
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const PixelType input = this->GetInputImage()->GetPixel( neighIndex ); |
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for(unsigned int k = 0; k < Dimension; k++ ) |
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{ |
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output[k] = static_cast<RealType>( input[k] ); |
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} |
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} |
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} |
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return ( output ); |
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} |
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} // namespace itk |
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#endif |
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