[Octave-bug-tracker] [bug #41480] image package :normxcorr2 yields different result from matlab

[anonymous]

Follow-up Comment #4, bug #41480 (project octave):

The deviation is not simply a matter of scaling. The normalized cross
correlation used in matlab is as defined in this article, formula (2):

http://scribblethink.org/Work/nvisionInterface/nip.pdf

This means, they use "centered 2nd moments" whereas the current implementation
in Octave uses "uncentered 2nd moments". Because the cross correlation itself
is given by the "uncentered mixed 2nd moment", the correlation coefficient (or
normalized cross correlation) is not simply given by a scaled cross
correlation. I suppose that the nomenclature creating the false impression
that these two quantities were related more closely is rather unfortunate.

(I will have a look at the tests when I have some more time.)

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