bugGNU Octave - Bugs: bug #52959, [octave forge] (image) histeq is...

 
 

bug #52959: [octave forge] (image) histeq is not compatible with Matlab

Submitter:  None
Submitted:  Tue 23 Jan 2018 05:58:57 PM UTC
 
Category:  Octave Forge Package Severity:  3 - Normal
Priority:  5 - Normal Item Group:  Matlab Compatibility
Status:  Confirmed Assigned to:  None
Originator Name:  Originator Email:  -email is unavailable-
Open/Closed:  * Open Release:  * dev
Operating System:  * GNU/Linux
* Mandatory Fields

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Tue 30 Jan 2018 10:51:34 PM UTC, comment #5: 

Thank you for the work around.

Anonymous
Sun 28 Jan 2018 09:21:21 PM UTC, comment #4: 

Checking again this bug report, indeed there is a problem of Matlab compatibility of histeq.
Thanks for reporting this.

Actually, there are few problems:

  • The output J should be in the same type as the input I. Now, even if I is uint8, J is double
  • Hist eq should support input image in types uint8, uint16, int16, single, or double.
  • There is an undocumented feature in Matlab: if histeq is called without argout, it displays (imshow) the output
  • Histeq can be called in matlab with J = histeq (I, hist) when is hist is a given histogram (input)
  • Histeq can be called in matlab with [J,T] = histeq (I) when is T is the calculated graylevel transformation (output)
  • Histeq can be called in matlab with map = histeq (I, oldmap)  to support an indexed image (I,oldmap)

Regarding the original report, a workaround can be:
J = histeq(grayimage16);
imshow(J);

A quick fix  for first 2 items, is to add the line
J = imcast(J, class(I))
Before endfunction.
A quick fix  for item 3, is to add the lines
If (nargout == 0)
 imshow(J)
end

Avinoam Kalma <avinoam>
Project Member
Sat 27 Jan 2018 05:07:04 PM UTC, comment #3: 

I will check the histeq issue, but pleay try
histeq(real(image))

Avinoam Kalma <avinoam>
Project Member
Wed 24 Jan 2018 08:39:39 PM UTC, comment #2: 

Hello
Thanks you have answered the second point, but I do not understand how this fixes the title of the bug.

Namely,
The histeq function is not returning results.
I had someone else try my code with matlab and it works. (See Fig 2 differences).

real(histeq(image))?
This does not make any changes. Am I misunderstanding?

Again thank you for the solution to the other issue. I had not searched for the bug as it was not my first concern. Maybe this was my fault for not making a bug report clear enough.

Anonymous
Wed 24 Jan 2018 06:04:34 PM UTC, comment #1: 

The problem is that  ifft(fft(x)) is not real for x real.
if you add real() in each fft you will get the rifht answers.

Closing as duplicate of bug #45932

Avinoam Kalma <avinoam>
Project Member
Tue 23 Jan 2018 05:58:57 PM UTC, original submission:  

Hello
I was using the image-2.6.1. Then updated to image-2.6.2 and received the same issues.

The histeq function is not returning results.
I had someone else try my code with matlab and it works. (See Fig 2 differences).

-----------------------------
Not sure if this should be another bug ticket
I am also having an issue with uint8?
I am receiving the following error:
error: invalid conversion from complex matrix to uint8

However, it could be the functions prior creating a complex matrix.

It does work on matlab (See Fig 9 differences)
I thought I would note the discrepancy,and maybe someone knows the issue.
-----------------------------

Note: I used https://savannah.gnu.org/patch/?func=detailitem&item_id=8722#options for impixelinfo (Andreas' version)

Anonymous

 

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file #43036:  DIP.zip added by None (1MiB - application/zip)

 

Depends on the following items: None found

Items that depend on this one: None found

 

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  • -email is unavailable- added by jwe (Updated the item)
  • -email is unavailable- added by avinoam
  • -email is unavailable- added by avinoam
  • -email is unavailable- added by avinoam (Posted a comment)
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    Follow 13 latest changes.

    Date Changed by Updated Field Previous Value => Replaced by
    2019-02-26 mtmiller Releaseother dev
        Summary [octave forge] (image) histeq is not compatible with Matlab [octave forge] (image) histeq is not compatible with Matlab
    2018-07-02 jwe Summary [octave-forge] (image) histeq is not compatible with Matlab [octave forge] (image) histeq is not compatible with Matlab
    2018-01-28 avinoam Summary[Image Package] histeq is not compatible with Matlab [octave-forge] (image) histeq is not compatible with Matlab
    2018-01-28 avinoam StatusDuplicate Confirmed
        Open/ClosedClosed Open
        Release4.2.1 other
        Summary[Image Package] histeq not returning results. [Image Package] histeq is not compatible with Matlab
        Carbon-Copy- Added hardy
        Carbon-Copy- Added carandraug
    2018-01-24 avinoam StatusNone Duplicate
        Open/ClosedOpen Closed
    2018-01-23 None Attached File- Added DIP.zip, #43036

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