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 Mar 6 19:43:58 2017  
 
Category: Octave FunctionSeverity: 3 - Normal
Priority: 5 - NormalItem Group: Incorrect Result
Status: NoneAssigned to: None
Originator Name: R.S.CarmenesOriginator Email: -unavailable-
Open/Closed: OpenRelease: 4.2.1
Operating System: GNU/Linux

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Sat Mar 11 19:11:37 2017, 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 Mar 6 19:43:58 2017, original submission:

Hi,

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).

Anonymous

 

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