[argyllcms] Re: Perceptual Reference Media gamut and ColProf
- From: Graeme Gill <graeme@xxxxxxxxxxxxx>
- To: argyllcms@xxxxxxxxxxxxx
- Date: Thu, 03 Nov 2011 00:58:06 +1100
Ignacio Ruiz de Conejo wrote:
> I think is a V2 profile, but I will check it, I may be wrong, thanks for the
> hint.
It's definitely V4.
> Defining it as input is precisely what i want to do. That way i will not
> compress the cyans, for
> instance, given that the inks I am using go far beyond the sRGB cyan.
But if your input images are in sRGB space, then there is no way that anything
can reach the larger cyans. ie., if you want to exercise the gamut, you need to
provide
an input that can reach the gamut edge.
> In other words, printing (0,255,255) and interpreting it as sRGB is
> delivering 40% of my cyan
> ink. But if I force it to be interpreted through the PRMG profile, I would
> use 100% of the
> cyan.
It's likely to have exactly the opposite effect. If the PRMG is bigger, it will
compress more to fit it in the destination space.
> Maybe -S is not the way to go, but now that I have explained what I want to
> accomplish (do not
> restrict the input images to be interpreted as sRGB, but expand its
> interpretation to use up all
> the ink gamut), how can we manage to do it, without V4 support?
By choosing to put your input images in a large gamut space, and then
specifying that
to colprof. But note that you can end up having the opposite effect to what
you want if you choose a colorspace that is larger than your output space,
and then use the colorspace gamut rather than the actual image gamut to
define your input gamut.
Another (more artificial) way of exercising the full gamut is simply to
use saturation intent rather than perceptual.
> In the end, obviously, what I am looking for is the RGB to CMYK transform,
> but without
> collapsing the colors between the ORMG and the ink gamut, as a normal link of
> the V2 profiles
> would do.
I'm not sure what you mean by this. The gamut mapping only compresses where it
has to,
given the definition of source and destination gamut.
Graeme Gill.
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