[Octave-bug-tracker] [bug #46099] image package: edge(I, 'canny') gives very bad quality results

[Carnë Draug]

Follow-up Comment #6, bug #46099 (project octave):

While trying to get some tests for canny (we have none at the moment so it
makes it tricky to test anything), I came up with a simplication of the
hysteresis step.  It seems to me that it can be replaced with imreconstruct
(or bwselect), like so:


-      bw = nonmax_supress(Es, Eo, thresh(1), thresh(2));
+      sup = nonmax_supress (Es, Eo);
+      bw = imreconstruct (sup > thresh(2), sup > thresh(1), 8); # hysteresis


My understanding of hysteresis is that this should be equivalent but running
some tests, I do not get the same values.  It may be a mistake on my part or
it may be that part of the bad quality results are also on the hysteresis
step.

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