Re: Rendering intents in source profiles?
Re: Rendering intents in source profiles?
- Subject: Re: Rendering intents in source profiles?
- From: Graeme Gill <email@hidden>
- Date: Thu, 24 Jul 2008 13:05:23 +1000
Uli Zappe wrote:
while working on the scanner profiling part of the Mac Life color
management review (I'll report the results when the new article will be
published), I wondered what rendering intents actually mean for source
profiles, i.e. for profiles whose A2Bn tags are used.
Welcome to the path of enlightenment :-)
For instance, take the classic example of a conversion from working
space to printer space. Since the printer space is smaller, gamut
compression or clipping obviously has to be performed. *But* this should
take place in the B2An tag of the printer profile (= target profile),
which "knows" about the limitations of the printer and can adjust the
gamut accordingly.
Oh, how can that work, since the output profile does not "know" what
input profile it is going to be linked to ?
[ Note that my ArgyllCMS profiler solves this problem by allowing
a source profile or gamut to be specified at output profile creation time.]
I don't see which role the working space profile (=
source profile) could actually play in its A2Bn tag, since the PCS will
by definition be able to represent all colors, so whatever colors the
working space comprises, there will be no need to perform gamut
compression or clipping when converting colors from the working space to
the PCS (which is what the A2Bn tag does).
My guess has always been that the the allowance for intent in the
A2B tables is part of a (flawed or at least limited) scheme
to make gamut mapping work in the ICC profile world, by allowing
the input profile to map the input device gamut to a "standard"
PCS gamut, and then have the output profile map from the PCS gamut
to the output device gamut. It's limitation is that it only
really works for (what I would call) saturation intent, since
the gamut surfaces will be mapped to gamut surface (expansion
of gamut as well as compression).
Up until an addendum to ICCV4 however (PRMG), there has been no standard
PCS gamut to make this scheme inter-operable between profiles from different
profile creation software.
Graeme Gill.
_______________________________________________
Do not post admin requests to the list. They will be ignored.
Colorsync-users mailing list (email@hidden)
Help/Unsubscribe/Update your Subscription:
This email sent to email@hidden