bugGNU Octave - Bugs: bug #54392, Matlab compatibility: syntax...


bug #54392: Matlab compatibility: syntax rgb2ind (img,N) to create a dithered image missing

Submitted by:  Rick T <ratulloch>
Submitted on:  Fri 27 Jul 2018 03:00:12 AM UTC  
Category:  Octave Function Severity:  1 - Wish
Priority:  3 - Low Item Group:  Feature Request
Status:  Confirmed Assigned to:  None
Originator Name:  Open/Closed:  Open
Release:  dev Operating System:  Any

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Sat 12 Jan 2019 04:48:25 PM UTC, comment #4:

See also patch #8001 reverted in bug #40669.

Guillaume <gyom>
Thu 06 Sep 2018 04:09:06 AM UTC, comment #3:

This bug tracker is for Octave, a free software program that implements most of the Matlab language. If you need to report a bug with Matlab you should visit the business that makes it: http://www.mathworks.com.

Rik <rik5>
Project Administrator
Wed 05 Sep 2018 11:21:03 AM UTC, comment #2:

I have found a bug in MATLAB where should I report it?
I have following an array structure:

S.X = some longitude
S.Y = some latitude values
S.Geometry = 'Point'
S.Field1 = "some characters'
S.Field2 = "some other characters'
S.Field3 = 12345
S.(Some other Fields) = 'some other stuff

And other problem:

I just create an image with Adobe Photoshop tool, I face an error as well as adobe photoshop error 16, how to solve this error, I share an error link https://www.adobesupportphonenumber.com/blog/fix-adobe-photoshop-error-16/

I also share an error attachment:

Ammy Watson <ammy>
Fri 27 Jul 2018 03:55:38 PM UTC, comment #1:

I'm not sure when Matlab added the calling form rgb2ind (img, N), but it was probably in the last 2-3 years.

I've changed the Summary to reflect the true issue. Someone who understands image processing will need to help on this issue and code up an initial implementation of the algorithm. Core developers can then polish it for performance and to adhere to Octave coding conventions.

Rik <rik5>
Project Administrator
Fri 27 Jul 2018 03:00:12 AM UTC, original submission:

I'm trying to create an animated gif using code I found at https://www.mathworks.com/matlabcentral/answers/94495-how-can-i-create-animated-gif-images-in-matlab

But I get an error
"error: Invalid call to rgb2ind. Correct usage is:

-- [X, MAP] = rgb2ind (RGB)
-- [X, MAP] = rgb2ind (R, G, B)

Additional help for built-in functions and operators is
available in the online version of the manual. Use the command
'doc <topic>' to search the manual index.

Help and information about Octave is also available on the WWW
at https://www.octave.org and via the -email is unavailable-
mailing list."

The code is below. Are there any workarounds?

h = figure;
axis tight manual % this ensures that getframe() returns a consistent size
filename = 'testAnimated.gif';
for n = 1:0.5:5
% Draw plot for y = x.^n
x = 0:0.01:1;
y = x.^n;
% Capture the plot as an image
frame = getframe(h);
im = frame2im(frame);
[imind,cm] = rgb2ind(im,256);
% Write to the GIF File
if n == 1
imwrite(imind,cm,filename,'gif', 'Loopcount',inf);

Nicholas Jankowski said the function is different from matlab and I should post a bug. See he's email he sent below

Looking at the function calling structure on matlab:


[X,map] = rgb2ind(RGB,n)
X = rgb2ind(RGB, map)
[X,map] = rgb2ind(RGB, tol)
[___] = rgb2ind(_,dither_option)

and octave:


[x, map] = rgb2ind (rgb)
[x, map] = rgb2ind (R, G, B)

it appears that the current Octave implementation is not fully compatible. Unless there's already something on the bug tracker that I didn't see in a quick search, it should probably be logged as one:

Rick T <ratulloch>


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  • -email is unavailable- added by gyom (Posted a comment)
  • -email is unavailable- added by jwe (Updated the item)
  • -email is unavailable- added by hardy
  • -email is unavailable- added by ammy (Posted a comment)
  • -email is unavailable- added by rik5 (Posted a comment)
  • -email is unavailable- added by ratulloch (Submitted the item)
  • -email is unavailable- added by ratulloch

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    Follow 8 latest changes.

    Date Changed by Updated Field Previous Value => Replaced by
    2019-01-12 jwe Priority5 - Normal => 3 - Low
        Item GroupMatlab Compatibility => Feature Request
    2018-10-06 hardy Carbon-Copy- => Added hardy
    2018-07-27 rik5 Severity3 - Normal => 1 - Wish
        StatusNone => Confirmed
        Release4.4.0 => dev
        Summaryrgb2ind issue and images / gif creation => Matlab compatibility: syntax rgb2ind (img,N) to create a dithered image missing
    2018-07-27 ratulloch Carbon-Copy- => Added -email is unavailable-

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