Description of problem:
xorg.conf has a Gamma setting:
Gamma red-gamma green-gamma blue-gamma
This is an optional entry that can be used to specify the gamma
correction for the monitor. It may be specified as either a
single value or as three separate RGB values. The values should
be in the range 0.1 to 10.0, and the default is 1.0. Not all
drivers are capable of using this information.
Since you can use this to adjust r/g/b levels separately, it might be nice to be able to create ICC profiles based on this.
Version-Release number of selected component (if applicable):
Author: Richard Hughes <firstname.lastname@example.org>
Date: Tue Sep 13 17:38:56 2011 +0100
Add --xorg-gamma to cd-create-profile to create custom gamma ramps
This allows power users to create a custom gamma curve using the same values
and in the same format that was set in xorg.conf.
This of course isn't profiling the screen, but it allows people to use a simple
color profile when they just want to use a fixed gamma scaling factor.
:100644 100644 ce60d93... 462c739... M client/cd-create-profile.c
:100644 100644 6573e52... d36f1b5... M data/Makefile.am
Grab http://people.freedesktop.org/~hughsient/temp/notting-80-80-60.icc is you don't feel like building from git master.
I tested this icc file... it's different in appearance to what I was getting from X.org.
Sep 13 14:12:13 <notting> airlied: i described gamma 0.8 to hughsie as 'set red/green/blue
channel to 80%'... is that not accurate?
Sep 13 14:15:51 <mclasen> gamma is a bit different from just a percentage
Sep 13 14:22:07 <notting> mclasen: it's not linear?
Sep 13 14:22:44 <mclasen> no
Sep 13 14:23:07 <mclasen> http://en.wikipedia.org/wiki/Gamma_correction
Sep 13 14:28:20 <notting> mclasen: ok, will talk to hughsie again tomorrow
(In reply to comment #2)
> Sep 13 14:12:13 <notting> airlied: i described gamma 0.8 to hughsie as
> 'set red/green/blue
> channel to 80%'... is that not accurate?
> Sep 13 14:15:51 <mclasen> gamma is a bit different from just a percentage
I did think it odd that the gamma wasn't a log function, but I implemented your spec to the letter :-)
I've switched the creator to use a standard gamma calculation, which I think gives you what you want. Can you try http://people.freedesktop.org/~hughsient/temp/notting-80-80-60-gamma.icc please, and tell me if this looks the same as it does from X.org.
No, it doesn't. What happens is that the cd-created profile is more 'washed out' than the X one.
Can you pinpoint where in X that gamma string is read, and how the gamma tables are constructed? I'm going to have to work out how X makes the gamma data from a single value if it's not a simple power log. Thanks.
I'll attempt to dig it up, in the meantime, cc'ing people who may know off the top of their head.
Ping? Got a link to that info?
Not yet, probably need to track down ajax or someone similar.
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