[Insight-users] Modifying Mattes MI to provide a Normalized MI

[Tomáš Kazmar]

Hi Jose,




(2) is one of the ways to compute mutual information, you get it from the 
definition by using the properties of log function and marginalization in 
the summands you get.





However, I think the class you want to create already exists, I havent used 
ITK for some time, but it should be called 
NormalizedMutualInformationHistogramImageToImageMetric.




Best,

T.



---------- Původní zpráva ----------
Od: Josem <jose at apollomit.com>
Datum: 26. 11. 2012
Předmět: [Insight-users] Modifying Mattes MI to provide a Normalized MI
"Hello, 
I have searched around the web for answers but i am still stuck with this
issue:
I am trying to modify the itkMattesMutualInformationImageToImageMetric.hxx
file to provide the Normalized Mutual Information.
I found this post:
http://public.kitware.com/pipermail/insight-users/2006-May/017911.html
(http://public.kitware.com/pipermail/insight-users/2006-May/017911.html)
Where they say that I should modify the lines 815-832, but i think the post
is outdated.

I also checked the GetValue() Method, and i think that's the method i have
to modify. But i can't figure it out.
Here are the lines where i think i should modify the code:

/**
* Compute the metric by double sumdation over histogram.
*/

// Setup pointer to point to the first bin
JointPDFValueType *jointPDFPtr =
this->m_ThreaderJointPDF[0]->GetBufferPointer();

PDFValueType sum = 0.0;
for( unsigned int fixedIndex = 0;
fixedIndex < this->m_NumberOfHistogramBins;
++fixedIndex )
{
const PDFValueType fixedImagePDFValue =
this->m_ThreaderFixedImageMarginalPDF[0][fixedIndex];
for( unsigned int movingIndex = 0;
movingIndex < this->m_NumberOfHistogramBins;
++movingIndex, jointPDFPtr++ )
{
const PDFValueType movingImagePDFValue =
this->m_MovingImageMarginalPDF[movingIndex];
const PDFValueType jointPDFValue = *( jointPDFPtr );

// check for non-zero bin contribution
static const PDFValueType closeToZero =
vcl_numeric_limits<PDFValueType>::epsilon();
if( jointPDFValue > closeToZero && movingImagePDFValue > closeToZero
)
{
const PDFValueType pRatio = vcl_log(jointPDFValue /
movingImagePDFValue);
if( fixedImagePDFValue > closeToZero )
{
sum += jointPDFValue * ( pRatio - vcl_log(fixedImagePDFValue) );
}
} // end if-block to check non-zero bin contribution
} // end for-loop over moving index
} 


But i don't know where should i modify the computation to do this:
(1) NMI = ( Ha + Hb ) / Hab
instead of this computation:
(2) MI = Ha + Hb - Hab

Basically i don't get where computation (2) is going on.

thanks in advance,
Jose





--
View this message in context: http://itk-users.7.n7.nabble.com/Modifying-
Mattes-MI-to-provide-a-Normalized-MI-tp30155.html
(http://itk-users.7.n7.nabble.com/Modifying-Mattes-MI-to-provide-a-Normalized-MI-tp30155.html)
Sent from the ITK - Users mailing list archive at Nabble.com.
_____________________________________
Powered by www.kitware.com(http://www.kitware.com)

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

Kitware offers ITK Training Courses, for more information visit:
http://www.kitware.com/products/protraining.php
(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(http://www.itk.org/Wiki/ITK_FAQ)

Follow this link to subscribe/unsubscribe:
http://www.itk.org/mailman/listinfo/insight-users
(http://www.itk.org/mailman/listinfo/insight-users)"
-------------- next part --------------
An HTML attachment was scrubbed...
URL: <http://www.itk.org/pipermail/insight-users/attachments/20121126/b30a031b/attachment.htm>