[argyllcms] Re: using targen with an existing profile
- From: "Roberto Michelena" <colorsync@xxxxxxxxx>
- To: argyllcms@xxxxxxxxxxxxx
- Date: Mon, 22 May 2006 10:20:04 -0500
-c doesn't do anything unless you specify a generation algorithm that
makes use of it, ie -R -I, or a -A value > 0.0
I see; so now I've just tested with all of them.
If you re-read the goal that the default algorithm is aiming for,
and have a think about what it means, then you will figure out that
yes, this results in sample points that aren't at the edges of the
device value gamut. This is because the edges are are being treated
the same as all other points, and are no worse off than a point in
the space equally far from several sample points.
Now it's quite reasonable to ask whether this is a good thing or not.
I haven't made up my mind myself, except so far as to force at least
the primary colorant values to be sampled by making the default
for -m 2. Certainly my testing didn't indicate that the profiles
accuracy is at all compromised by the lack of sample points lying
on the gamut boundary, but I have wondered whether this leaves things
open to unanticipated problems.
(I hope this makes some kind of sense!)
this is weird... how can you do correct perceptual mapping if you
don't have a clear idea of your gamut boundary? and how can you define
your gamut boundary without sampling it?
usually the problem with ICC standard linking lies in the gamut
borders; that is something -G solves, but only if it does have
accurate info on that part of the space, wouldn't it be so?
what I'd like is something like filling the space very densely with -m
(say, 64,000 points), then delete all points over the ink limit, then
convert to Lab via the pre-existing profile, put a 3D grid (of cubes
or tetrahedrons, whatever) in Lab space and inside of each grid volume
compartment, delete all the points except the one closest to the
center of the compartment; exception being any point which has 100% of
at least one colorant or which is at the surface of the volume defined
by all the points (the gamut volume).
this is more or less what I was expecting from targen -c ; obviously
I'm still lagging behind in comprehension :) bear with me, just
started playing with Argyll.
-- Roberto Michelena
Infinitek
Lima, Peru
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