[argyllcms] Re: dispwin vs xcalib loading LUT

Stefan,

so my assumtion regarding xcalib was wrong ;-)

Nevertheless a curve computed with gamma 2.2 will not be the same as a 
curve with parametric gamma 2.2. Thats indeed wired.

Would this mean to avoid the parametric form of vcgt gamma specifying 
enirely to avoid such confusion.

By the way the Lindbloom profiles are no real world cases and difficult 
as we can see here?

Thanks for sheeding light on this matter.

regards
Kai-Uwe Behrmann
--
development for color management 
www.behrmann.name + www.oyranos.org + www.cinepaint.org


Am 01.01.07, 13:22 +0100 schrieb Stefan Döhla:

> I am, however I'm not the author of dispwin ;-)
> 
> When I started xcalib, I crosschecked with some other calibration
> loaders to find out why gamma 1.0 in the vcgt tag makes the screen
> darker when using these other loaders - 1.0 was supposed to mean
> linear ...
> 
> Therefore I took the system gamma into account, which is 2.2 on Win32
> and 2.222 on Unixes - voila: results were the same!
> 
> The ramp is then created from the gamma values rGamma, rMax and rMin like 
> this:
> 
> for(j=0; j<nEntries;j++)
> {
>   ramp[j] = 65536.0 *
>           pow (j * (rMax - rMin) / nEntries, rGamma * SYSTEM_GAMMA)
>           + rMin);
> }
> 
> I think xcalib's behaviour is correct - at least if the
> result is compared to other calibration loaders like the WindowsXP
> color panel, ...
> 
> Happy new year everyone
> Stefan
> 
> --
> mailto:color@xxxxxxxxx
> 
>

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