[argyllcms] Re: RGB printer profiling, A2B tables

  • From: Graeme Gill <graeme@xxxxxxxxxxxxx>
  • To: argyllcms@xxxxxxxxxxxxx
  • Date: Fri, 12 Jan 2007 23:37:04 +1100

Klaus Karcher wrote:

AFAIK that's what Heidelberg advertises as "Inverse [sic] Gamut Mapping".

Right, so it may be a Heidelberg feature, but other packages may
take another approach. Currently I'm happy that Argyll's approach
is at least consistent and functional, and I feel no inclination
to change it's ICCV2 behaviour.

In my humble comprehesion, the PRMG (http://www.color.org/ICCSpecRevision_22_02_05_PRMG.pdf) is (or shoud be?) a agreed-upon determination of the PCS gamut boundary and a perceptual gamut mapping should map the source gamut to the PRMG without clipping in a "pleasant" way (however defined). In addition, it needs a vendor independent, invertible gamut mapping algorithm to be of use. If the user wants clipping, he has to boost the chroma of the source image to exceed the PRMG limits. Did I miss or fail to see something?

The reference gamut is still to a degree "work in progress". It may
not change at this stage, but it's possible it might to some degree,
since there has been more analysis and some criticism of it since
it has been made public.

As for a standard gamut mapping algorithm, I hardly see that as
desirable. Gamut mapping is very definitely still a research
topic, and will almost certainly be one for many year to come.
It's just not desirable to anoint one in a standard.
This situation is hardly surprising, since gamut mapping is
at least 50% art and taste, not science. Do you
really want color management to be frozen at the state of
the art 2005, rather than further improving ? It would be
far wiser I think, to settle on standards that don't depend
on standardizing a gamut mapping algorithm for their
interoperabillity.

cheers,

Graeme Gill.

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