bugGNU Octave - Bugs: bug #45333, [octave forge] (image) graythresh...

 
 

bug #45333: [octave forge] (image) graythresh fails if input doesn't have different values

Submitter:  Carnë Draug <carandraug>
Submitted:  Tue 16 Jun 2015 06:10:56 PM UTC
 
Category:  Octave Forge Package Severity:  3 - Normal
Priority:  5 - Normal Item Group:  Inaccurate Result
Status:  Fixed Assigned to:  carandraug
Originator Name:  Open/Closed:  * Closed
Release:  * dev Operating System:  * Any
* Mandatory Fields

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Fri 19 Oct 2018 10:58:05 AM UTC, comment #13: 
Avinoam Kalma <avinoam>
Project Member
Tue 16 Oct 2018 07:38:18 PM UTC, comment #12: 

Please review the attached cs which handles comment #9 & comment #10

(file #45212)

Avinoam Kalma <avinoam>
Project Member
Tue 28 Nov 2017 08:20:20 PM UTC, comment #11: 

Reopening this bug, because of comment #9 and comment #10 that should be fixed.

Avinoam Kalma <avinoam>
Project Member
Tue 06 Jun 2017 08:46:26 PM UTC, comment #10: 

There is another problem with graythresh:
running the tests with Otsu in Matlab, the thresh is 114.5, and not 115, so the test should be:

%!assert (graythresh (img, "otsu"),            114.5/255);
%! histo = hist (img(:), 0:255);
%!assert (graythresh (histo, "otsu"),          114.5/255);

To get Matlab results, the "ceil" in line 235 should be removed.

Avinoam Kalma <avinoam>
Project Member
Mon 05 Jun 2017 09:10:33 PM UTC, comment #9: 

There is still a minor problem in a corner case:

>> H(1) = 100;
>> graythresh(H)
warning: division by zero
warning: called from
    graythresh>otsu at line 217 column 13
    graythresh at line 186 column 35
warning: division by zero
warning: called from
    graythresh at line 192 column 12
ans = NaN

In Matlab the answer is zero.
The problem is in the line:

  thresh{1} = double (thresh{1}) / (numel (ihist) - 1);

since numel(ihist) is 1

Avinoam Kalma <avinoam>
Project Member
Sun 23 Apr 2017 08:34:40 PM UTC, comment #8: 
Carnë Draug <carandraug>
Project Member
Sun 23 Apr 2017 06:00:22 PM UTC, comment #7: 

Another typo:

 img_max = 65535 in line 171, but img_max is not used elsewhere.

Avinoam Kalma <avinoam>
Project Member
Wed 12 Apr 2017 04:41:25 PM UTC, comment #6: 

> It seems that few semicolons have disappeared.


Ups.  I put them back now

http://hg.code.sf.net/p/octave/image/rev/382986039e12

Carnë Draug <carandraug>
Project Member
Wed 12 Apr 2017 02:13:55 PM UTC, comment #5: 

@Carnë: Thanks for the fix.
It seems that few semicolons have disappeared.

Avinoam Kalma <avinoam>
Project Member
Wed 12 Apr 2017 01:27:33 PM UTC, comment #4: 

I am not sure why you were using `!isfinite` when the problem is that `max (bcv)` returned NaN.  I used isnan which is clearer.  Also, I put the check earlier and avoided computing threshold and goodness in such case.

http://hg.code.sf.net/p/octave/image/rev/34c55ccd6dad

Carnë Draug <carandraug>
Project Member
Thu 08 Dec 2016 05:36:22 PM UTC, comment #3: 

@Carnë:

Please review the cs in comment #2

Avinoam Kalma <avinoam>
Project Member
Wed 19 Aug 2015 08:20:56 AM UTC, comment #2: 

cs attached. Please review

(file #34676)

Avinoam Kalma <avinoam>
Project Member
Wed 17 Jun 2015 05:57:42 AM UTC, comment #1: 

The correction should be something like

if (~isfinite(max(bcv)))
     thresh{1} = 0;
     thresh{2} = 0;
endif

near the end of function otsu

Avinoam Kalma <avinoam>
Project Member
Tue 16 Jun 2015 06:10:56 PM UTC, original submission:  

Example:

octave> a = repmat (0.5, 100, 100);
octave> graythresh (a)
ans = [](1x0)

For Matlab compatibility, such corner case should return a value of zero.

Carnë Draug <carandraug>
Project Member

 

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Attach Files:
   
   
Comment:
   

Attached Files
file #45212:  graythresh.cs added by avinoam (3KiB - text/plain)
file #34676:  bug45333.cs added by avinoam (703B - text/plain)

 

Depends on the following items: None found

Items that depend on this one: None found

 

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    Follow 14 latest changes.

    Date Changed by Updated Field Previous Value => Replaced by
    2018-10-19 mtmiller Carbon-CopyRemoved 80942 -
    2018-10-19 avinoam Open/ClosedOpen Closed
    2018-10-19 avinoam StatusPatch Submitted Fixed
    2018-10-16 avinoam Attached File- Added graythresh.cs, #45212
        StatusIn Progress Patch Submitted
    2018-03-20 mtmiller Summary[octave forge] (image) grayhresh fails if input doesn't have different values [octave forge] (image) graythresh fails if input doesn't have different values
    2018-03-20 mtmiller Summaryimage package: grayhresh fails if input doesn't have different values [octave forge] (image) grayhresh fails if input doesn't have different values
    2017-11-28 avinoam StatusFixed In Progress
        Open/ClosedClosed Open
    2017-04-12 carandraug StatusPatch Submitted Fixed
        Open/ClosedOpen Closed
    2017-03-06 avinoam StatusNone Patch Submitted
    2016-12-08 avinoam Carbon-Copy- Added -email is unavailable-
    2015-08-19 avinoam Attached File- Added bug45333.cs, #34676

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