Davyd ([info]davyd) wrote,
@ 2008-03-18 20:41:00
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straight, no chaser (colour management in GNOME)
After playing with Gimp 2.4's automagic white balance correction and then wondering about how realistic the colours on my monitor were, I was having a look at colour profile management in Linux tonight.

I knew about XICC, which sets the per monitor colour profile that applications can utilise, but of course this needs an ICC file. Argyll CMS can generate an ICC profile if you have one of those fancy colourimeters, but how do you generate a rough profile without one? I had a look at LPROF, but I could not figure out how it works.

It seems to me that with a significant number of GNOMEy apps supporting colour profiles via XICC (Firefox 3, Eye of GNOME, Gimp, Inkscape), that it would be really awesome for GNOME to provide some colour profile support. I figure this would have two parts. Firstly, a management tool that stored ICC profile files and allowed you set a colour profile for a monitor (combined with gnome-settings-daemon loading these profiles on startup). Secondly a colour calibration tool. This would primarily be a tool for amateurs who wanted rough colour calibration, but didn't want to go out and purchase a calibration device (i.e. me). Support for colourimeters would be nice, but in my opinion, a secondary concern.

To provide a reference, I've taken some screenshots of how the colour calibration ("expert mode") works in MacOSX.

Colours are something that I practically know nothing about, I don't understand why each of the 5 calibration dialogs is important or why they work or what they're setting, but I think this sort of clear, pedagogic calibration system, combined with some profile management (perhaps in a new XRandR enabled monitor setup dialog page) is what's needed, and would be a really awesome addition to GNOME.


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[info]matt.ucc.asn.au
2008-03-18 11:55 am UTC (link)
For figuring curves for RGB, the interface of the OS X program "Supercal" ( http://www.bergdesign.com/supercal/ ) seems better than Apple's approach.

Doing white balance by eye seems hard though.

Good colour support in Linux would rock, though I suspect you'd really need the video hardware to be playing a part for it to be quick.

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[info]davyd
2008-03-18 11:59 am UTC (link)
I think most of the technology components are in place for Linux colour support, just there is no management UI (you need to run `xicc` in some sort of startup script) and no nice ICC profile creator.

I don't know how much more needs adding to X11. Some possibly.

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(Anonymous)
2008-03-18 12:16 pm UTC (link)
You can adjust, calibrate without a colourimeter, but not profiling (and so creating an icc profil) without it.

Take a look at http://www.pcbypaul.com/software/GAMMApage.html or http://www.pcbypaul.com/software/monica.html for first steps (https://wiki.ubuntu.com/MOTU/Teams/Photo for links on photography softwares).

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[info]prokoudine
2008-03-18 12:21 pm UTC (link)
I had a look at LPROF, but I could not figure out how it works.

And you didn't read docs? :)

BTW, generating "rough profiles" doesn't make a lot of sense. Get at least a Huey or, better, an i1 Display LT and LProf/CVS.

More on this: http://prokoudine.info/blog/?p=68

Color management is among SoC ideas this year and hopefully someone will take this. We DO need it, yes :) But I'd say that xcalib and ArgyllCMS that are mentioned in the wiki are not the way to go.

OpenICC has a project idea to create a library from Oyranos. Checkout http://www.freedesktop.org/wiki/OpenIccForGoogleSoC2008

A wide adoption of Oyranos means sharing color management settings between applications. This is IMO how it should work.

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[info]davyd
2008-03-18 12:59 pm UTC (link)
I looked at the in-app help, but it didn't make a lot of sense to me still.

Perhaps I'm talking out of my arse, because I don't really get how colour calibration works and what's required, but why doesn't having a rough profile make a lot of sense?

Basically, I'm trying to avoid going out to buy a calibration device at this experimentation stage. Maybe I know someone who already owns one.

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Not only for GNOME?
(Anonymous)
2008-03-18 12:27 pm UTC (link)
It would be even more awesome if this could be done on the FreeDesktop level instead of just for GNOME. How about some cooperation here?

-Inge Wallin

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Re: Not only for GNOME?
[info]davyd
2008-03-18 12:29 pm UTC (link)
Sure, I don't see why that could be the case.

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(Anonymous)
2008-03-18 12:30 pm UTC (link)
Maybe shiping icc profiles for laptops / Auto-detactable screens. No need for manual tuning in most cases?

OS X ship with ICC profiles needed, i remember a very old CRT screen also came with them.

Maybe there are other reasons this isn't possible?

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[info]davyd
2008-03-18 01:01 pm UTC (link)
I googled for an ICC profile for my laptop, but I didn't find one. I didn't think it worked like that.

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on color management
(Anonymous)
2008-03-18 05:26 pm UTC (link)
Hi there

Color management includes different parts: your image file (is it AdobeRGB or sRGB), your monitor (has to be calibrated), your image software (has to be color management aware) and your printer / printing software. Hence the idea of color management system.

If you don't see why you need it for, better stay away from it than messing with it - it can be very frustrating very quickly. However, a color managed system that works well is pure joy.

FYI, I am maintaining a blog on Linux & photography and I have a few entries that could help getting an idea on the subject: http://jcornuz.wordpress.com/category/tutorials/

Take care,

Joel

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Re: on color management
[info]davyd
2008-03-19 12:13 am UTC (link)
The reason I started playing with it was that the other day I used Gimp
to apply some colour correction and white balance compensation to a
digital photo that I took. I then had that digital photo printed at a
print shop. The photo turned out ok, but it demonstrated how the colour
representation of my LCD was not quite equivalent to the printer.

So hence I start trying to learn about colour management. It seems to
me that the camera is likely to write colour management information
into the file (although unlike a scanner, the camera's representation
of colour would undoubtedly depend on many variables you can't always
control for). I assume that a professional printer also has colour
calibrated machines. So the same photo straight from the camera should
print the same on two identical machines, but then there is my LCD...
if that's not calibrated then what I see on the screen may not prove to
be the same as what comes out of the printer.

The thing is, at this stage I'm not trying to get too serious, I was
more hoping to be able to get a 'general idea' of how it would be
printed.

I guess the point is that I'm very much a 'user' in this instance,
because I don't have professional requirements or understand the
technicalities of colour management, and that it seems that today on
X-based desktops, colour management is not really for users.

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Re: on color management
(Anonymous)
2008-03-19 02:58 pm UTC (link)
Hi there,

If you add a "professional printer" to the mix, it gets even more delicate ;-)
The result may vary from one lab to another or even from whom operates the machine - and it will be very hard to know who to blame: your LCD, the lab or the operator...
At that stage it is a trial and error thing and it would probably be the same on Windows.

Take care,

Joel

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Re: on color management
[info]davyd
2008-03-20 06:08 pm UTC (link)
Indeed, there were a couple of blue blemishes on the print that I'm pretty sure are entirely their creation.

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[info]zdzichu.openid.pl
2008-03-18 06:38 pm UTC (link)
I too was under impression that color profile file is provided by monitor manufacturer. For example, for LCD in my ThinkPad there is TPLCD.ICM file.

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[info]davyd
2008-03-19 12:02 am UTC (link)
Perhaps I should look on my Windows partition.

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