[Octave-bug-tracker] [bug #46547] image package: canny detector in edge() should use LoG as first step

[Hartmut]

Follow-up Comment #3, bug #46547 (project octave):

I've just filed a PATCH to fix the issue of bug #46099. I suspect that this
could fix the issue in this bug report as well. 

Could someone please test, if the mentioned patch improves or solves the
situation here as well?

There might still be some difference in the automatic computation of threshold
values, if you don't give them explicitly. But otherwise I hope this  patch
will make the Canny method in edge.m behave much more like its Matlab
counterpart.

Note: Further investigation showed, that Matlab does NOT use LoG filtering as
a first step in the Canny edge detector. They weren't saying this clearly in
their documentation, but now I'm pretty sure they are also doing a Prewitt
filter as a first step. I think they only had a bug in their old
implementation (now in "canny_old" method). Sorry for the confusion!

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