[Octave-bug-tracker] [bug #52555] [octave forge] (image) Failing unit test for bwconncomp

[Rafael Laboissiere]

URL:
  <http://savannah.gnu.org/bugs/?52555>

                 Summary: [octave forge] (image) Failing unit test for
bwconncomp
                 Project: GNU Octave
            Submitted by: rlaboiss
            Submitted on: Thu 30 Nov 2017 05:35:27 AM UTC
                Category: Octave Forge Package
                Severity: 3 - Normal
                Priority: 5 - Normal
              Item Group: Incorrect Result
                  Status: None
             Assigned to: None
         Originator Name: 
        Originator Email: 
             Open/Closed: Open
         Discussion Lock: Any
                 Release: other
        Operating System: Other

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Details:

One of the unit tests for function bwconncomp is failing randomly:


octave:1> pkg load image
octave:2> while 1
   a = rand (40, 40) > 0.2;
   cc = bwconncomp (a, 4);
   assert (columns (cc.PixelIdxList) > 1)
endwhile
error: assert (columns (cc.PixelIdxList) > 1) failed
error: called from assert at line 92 column 11


The image matrix "a" generated with the rand function may contain a single
connected object.  For instance:


octave:1> pkg load image
octave:2> n = 1000;
octave:3> c = repmat (NA, n, 1);
octave:4> for i = 1 : n
    a = rand (40, 40) > 0.2;
    cc = bwconncomp (a, 4);
    c (i) = columns (cc.PixelIdxList);
endfor
octave:5> length (find (c <= 1))
ans =  24


Increasing the threshold, drastically reduces the failure rate, for instance:


a = rand (40, 40) > 0.3;






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