[Octave-bug-tracker] [bug #50151] image package: normxcorr2 is not compatible with Matlab

[Hartmut]

Follow-up Comment #1, bug #50151 (project octave):

It might be a non-trivial task to fix this:

Matlab sometimes does calculations in the spatial or the frequency domain, it
sounds quite convoluted:

Algorithms

normxcorr2 uses the following general procedure:

1. Calculate cross-correlation in the spatial or the frequency domain,
depending on size of images.

2. Calculate local sums by precomputing running sums.

3. Use local sums to normalize the cross-correlation to get correlation
coefficients. 

(see http://de.mathworks.com/help/images/ref/normxcorr2.html#f6-308857)

In contrast, the Octave version of normxcorr2 does simply use the convn
function, always in the spatial domain.

Question: Are there also significant differences between Matlab and Octave
output for "center pixels"? I mean differences for pixels that are further
away from the image border than the width of the template? Or is this always
only an issue for pixels near the image border?

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