New reason for XYZ

[Kai-Uwe Behrmann]

Am 07.03.07, 12:15 +0100 schrieb Cyrille Berger:

> > The difficulty arrises by the usable points in the conversion LUT. As XYZ
> > is very huge, the used point in the transforming LUT to tell about the
> > right transistion are a few only. With fewer points less accuracy ...
> >
> > To visualise look at the devicelink tables in ICC Examin.
> Hum, but isn't XYZ use as a PCS ? I mean when doing color transformation, 
> don't we do something like RGB -> XYZ -> ( eventually LAB) -> something 
> else ? So RGB -> XYZ -> RGB should return the same value, or have I missed 
> something (which is surely the case ;) ) ?

RGB -> XYZ LUT profile are rare. XYZ matrix ones can be precalculated in 
floating point precision. The final device link used by lcms for the 
colour transformation is RGB -> RGB. 
The imprecision with 8- and 16-bit starts where one have to do a 
deviceRGB/CMYK <-> XYZ conversion with a LUT involved.

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