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[Octave-bug-tracker] [bug #47879] image package: imerode and imdilate se


From: Carnë Draug
Subject: [Octave-bug-tracker] [bug #47879] image package: imerode and imdilate sets elements to Inf when SE is zero
Date: Tue, 10 May 2016 17:42:54 +0000 (UTC)
User-agent: Mozilla/5.0 (X11; Linux x86_64; rv:38.0) Gecko/20100101 Firefox/38.0 Iceweasel/38.8.0

Update of bug #47879 (project octave):

                Category:    Octave Forge Package => Octave Function        
                  Status:                    None => Invalid                
             Open/Closed:                    Open => Closed                 
                 Release:                   4.0.0 => other                  
        Operating System:       Microsoft Windows => Any                    

    _______________________________________________________

Follow-up Comment #2:

I added several new test cases to imdilate and imerode.

http://hg.code.sf.net/p/octave/image/rev/e959fc1c7b0a

Some of them were failing but I have now push other changes so that they all
pass and works coherently, i.e., when erosion or dilation get an empty set,
they return that type maximum and minimum value. This should happen if SE is
both an empty or blank, and also in cases where all of the SE would be outside
the image (different cases in the code but mathematically need to behave the
same).

>From Artur Wegele via email:
> Should the function throw an exception, when the structuring element has a 0
overlapping with the image as in my case?
>
> I think the result is undefined same as if we divide 0/0. I expect imerode
to deliver only values found in the source image. If there is no overlapping,
then it can't work correctly.

If you are worried about this cases while at the same create unusual shaped
SE, you can use the "valid" option of imerode.

---

I'm closing as invalid since after looking more into literature, Inf and -Inf
can be considered correct valid. See
http://stackoverflow.com/a/37117842/1609556

    _______________________________________________________

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