[argyllcms] Re: WCS Gamut mapping strategies

Hi Graeme,

sorry for being unprecise.

First of all, they perform gamut maping in CIECAM02 Jab.
They take a look on every devices "grey", which must not
necessarily be on the J axis.
They look how much this special grey point must be moved
so it gets to lie on the J neutral axis.
Then they move every color of the gamut the same way as
they did with the grey point with the same L.

Then they perform gamut mapping and after that they do
the inverse with the destination gamut

There is a picture in the following PowerPoint document
on page 18

http://download.microsoft.com/download/f/0/5/f05a42ce-575b-4c60-82d6 -208d3754b2d6/ColorMgmt_Ecosystem.ppt

Regards

Rolf

Am 05.04.2006 um 11:53 schrieb Graeme Gill:

Rolf Gierling wrote: 
in a techdoc regarding WCS Gamut mapping strategies
I've found that Windows Color System will match the
whole grey axis on to each other.


It depends a lot on the details. By "whole grey axis", do
you mean the white point to the black point ?

Where does the black point come from ? There are lots of
ways of choosing a black point. It might be the darkest point
that is achievable in a gamut. It might be the darkest point
in the black ink chromatic direction that can be achieved in
a gamut (that's what Argyll's profile does for CMYK devices.)
It might be the darkest point in the line between the white point
and Lab 0,0,0. All these "lines" and "directions" might be in
XYZ, L*a*b*, CIECAM02 Jab, or some other colorspace.

Are you referring to "perceptual" intent (or something analogous) ?

(I expect it may be a bit difficult to pin down the answers to
these questions from the available WCS documentation !)

Graeme Gill.






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