bugGNU Octave - Bugs: bug #50471, imshow(I,[]) or imshow(I,[a b])...


bug #50471: imshow(I,[]) or imshow(I,[a b]) fail to scale intensities with RGB images

Submitted by:  None
Submitted on:  Mon 06 Mar 2017 07:43:58 PM UTC  
Category:  Octave Function Severity:  3 - Normal
Priority:  5 - Normal Item Group:  Incorrect Result
Status:  None Assigned to:  None
Originator Name:  R.S.Carmenes Originator Email:  -email is unavailable-
Open/Closed:  Open Release:  4.2.1
Operating System:  GNU/Linux

Add a New Comment(Rich Markup)

You are not logged in

Please log in, so followups can be emailed to you.


Sat 11 Mar 2017 07:11:37 PM UTC, comment #1:

When I read the Matlab help on "imshow", then I think this is INTENTIONAL behavior.

The Matlab help https://de.mathworks.com/help/matlab/ref/imshow.html#inputarg_DisplayRange
reads like this:

So the display range can only be adjusted for GRAYSCALE images, not for COLOR images. (I don't know of a unique and easy way to define a "minimum" or a "maximum" value of an rgb-color image either.)

Maybe we could state this fact more clearly in the Octave help string of imshow.m as well. It currently reads:

We might add the following sentence at the end of this part of the help text: "(The LIMITS option only has an effect on the display of grayscale images, it will be ignored for color images.)"

Hartmut <hardy>
Mon 06 Mar 2017 07:43:58 PM UTC, original submission:


imshow(I, []) and imshow(I, [a b]) fail to rescale display intensities (= has no effect whatsoever on display) when I is a color image of any type (uint8, uint16, single or double).

It works as expected with gray images though.

The problem appears at least with octave-4.0.3 and octave-4.2.1 and with or without image package loaded, and with at least the gnuplot and fltk graphics_toolkit (did not try the qt).



(Note: upload size limit is set to 16384 kB, after insertion of the required escape characters.)

Attach Files:

No files currently attached


Depends on the following items: None found

Items that depend on this one: None found


Carbon-Copy List
  • -email is unavailable- added by hardy (Posted a comment)
  • -email is unavailable- added by None (Submitted the item)

    Do you think this task is very important?
    If so, you can add your encouragement to it.
    This task has 0 encouragements so far.

    Only project members can vote.




    No changes have been made to this item

    Back to the top

    Powered by Savane 3.3