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[Octave-bug-tracker] [bug #44385] image package: simple gamma correction

From: H. G.
Subject: [Octave-bug-tracker] [bug #44385] image package: simple gamma correction with imadjust fails
Date: Fri, 27 Feb 2015 19:35:53 +0000
User-agent: Mozilla/5.0 (X11; Ubuntu; Linux x86_64; rv:36.0) Gecko/20100101 Firefox/36.0


                 Summary: image package: simple gamma correction with imadjust
                 Project: GNU Octave
            Submitted by: hardy
            Submitted on: Fr 27 Feb 2015 19:35:52 GMT
                Category: Octave Forge Package
                Severity: 3 - Normal
                Priority: 5 - Normal
              Item Group: Incorrect Result
                  Status: None
             Assigned to: None
         Originator Name: 
        Originator Email: 
             Open/Closed: Open
         Discussion Lock: Any
                 Release: 3.8.2
        Operating System: Any



Here is a small script to show the behavior:

close, clear all;
I = [0 0.5; 0.3 1];
gamma = 3;
J = imadjust(I, [], [], gamma);

With Octave 3.8.2 and the image package in version 2.2.2 the last command
results in an error message.

With Matlab this kind of easy gamma correction works fine, as you can see here
for example: http://de.mathworks.com/help/images/contrast-adjustment.html

In the Octave help text of the function imadjust.n it is stated, that the
second argument, as well as the third argument, default to [0 1] if not
specified. But in this case this seems NOT to happen. The correct result as
produced by 

J = imadjust (I, [0 1], [0 1], gamma)

is not returned.

Further tests show, that the second argument of imadjust properly defaults to
[0 1] if not given, but the third argument does NOT.


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