[ITK] [ITK-users] Computation of the derivative of normalized cross correlation

[C Boydev]

Hi everyone,

I'm trying to understand the implementation of 
itkNormalizedCorrelationImageToImageMetric. I understand the use of the 
jacobian and the gradient of the moving image to calculate the 
differential but I don't see why we don't have
derivative[i] = derivativeF[i]  / denom instead of derivative[i] = ( 
derivativeF[i] - ( sfm / smm ) * derivativeM[i] ) / denom in the final loop:


if( this->m_NumberOfPixelsCounted > 0 && denom != 0.0 )
     {
     for( unsigned int i = 0; i < ParametersDimension; i++ )
       {
       derivative[i] = ( derivativeF[i] - ( sfm / smm ) * derivativeM[i] 
) / denom;
       }
     }


I must be missing something - where does the term ( sfm / smm ) * 
derivativeM[i] come from?

Thank you very much for your help,
Christina

-- 
PhD student
Phone: +41 78 661 65 33

Laboratoire de Traitement des Signaux 5 - EPFL-STI-IEL-LTS5
Ecole Polytechnique Fédérale de Lausanne
ELD 231 Station 11 - CH 1015 Lausanne Suisse

Laboratoire d'Automatique, de Mécanique et d'Informatique Industrielles et Humaines - LAMIH CNRS UMR 8201
Université de Valenciennes et du Hainaut-Cambrésis
Le Mont-Houy 59313 Valenciennes Cedex 9 France

_____________________________________
Powered by www.kitware.com

Visit other Kitware open-source projects at
http://www.kitware.com/opensource/opensource.html

Kitware offers ITK Training Courses, for more information visit:
http://www.kitware.com/products/protraining.php

Please keep messages on-topic and check the ITK FAQ at:
http://www.itk.org/Wiki/ITK_FAQ

Follow this link to subscribe/unsubscribe:
http://public.kitware.com/mailman/listinfo/insight-users