[argyllcms] Re: Eye of Gnome Color Management

  • From: "Hal V. Engel" <hvengel@xxxxxxxxxxx>
  • To: argyllcms@xxxxxxxxxxxxx
  • Date: Mon, 30 Mar 2009 17:54:30 -0700

On Monday 30 March 2009 02:28:01 pm Leonard Evens wrote:
> I have been confused about whether or not Eye of Gnome, under Linux,
> supports color management.  There seemed to be several bits of seemingly
> contradictory evidence.
>
> 1.  eog definitely shows something different on the display from what
> gimp, inkscape, and Firefox, all of which agree, show. The last three
> programs can be configured to get the display profile from from the
> system, and they show exactly the same thing for any image file.   If I
> tell those  programs not to use the display profile, then what they show
> looks exactly like what eog shows.
>
> 2.  Searching the source code for eog does bring up icc strings.   I
> believe it may also show it making an attempt to get the profile from
> the system, but I'm not sure about that.   I didn't try to actually
> understand the code, looking instead just at function calls which seemed
> relevant.
>
> 3.  At the suggestion of a couple of previous responses to my posts, I
> tried looking at certain test files as recommended, and the results
> seemed to confirm that eog was using color management information.
>
> 1 seems inconsistent with 2 and 3.   But I believe I may have discovered
> one possible source.    Searching the eog development archives, I found
> notes to the effect that color management only worked for files with
> imbedded color profiles.  (This is considered a defect.)

This condition is not defined by any standard since one part of the transform 
is not defined (IE. the missing embedded profile).  But in some cases 
applications will make the assumption, and we all know what they say about 
assumptions, that any image with no embedded profile is some "standard" color 
space like sRGB but this could also be wrong.  Think of it like this:

Given 

X + Y = Z and Y = 5 

how would you figure out what Z is?  Of course you can't and this is analogues 
to: 

Image with no embedded profile (X) transformed into (+) the monitor color 
space (Y) = the transformed image (Z ?? who knows what this should be).   

To solve for two unknowns you need at least two equations involving those 
unknowns and in this case there is only one equation.

> I don't know
> if that means it uses only the imbedded profile or if it means that it
> will only make use of the system display profile if there is a profile
> of any sort imbedded in the file, e.g, an sRGB profile.    It may be
> that the image files I've been testing with don't have imbedded
> profiles.
>
> Any comments?


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