Re: ICC v4
Re: ICC v4
- Subject: Re: ICC v4
- From: Roger Breton <email@hidden>
- Date: Fri, 18 Nov 2005 21:28:59 -0500
>> That's a big part of the problem with ICC v2 is that the destination
>> profile's
>> gamut compression is pre-baked at the time it's built, rather than being
>> dynamically computed based on the gamut of the source profile.
>
> I want to make sure I understand this correctly, and that the above
> statement is not interpreted to mean what it doesn't say.
>
> This is how I read it:
>
> The gamut "compression dynamics" are currently set in stone inside profiles,
> one-size-fits-all style,
Marco,
The way I understand this, in non-technical terms, is that the gamut
compression -- only applicable in my view to the Perceptual intent, in my
view -- is calculated at the time of creating the profile, say in
ProfileMakerPro or Argyll. What this means is that the profiler calculates a
fixed solution from the entire ICC Lab space lattice which has, by
definition, extend all the way from 0 < L* < 100, -127 < a* < +127 and -127
< b* < +127. So it's a fixed transform or rather "mapping" from the whole
PCS Lab to whathever device coordinates like CMYK. So you see, in this
scheme of things, the characteristics of either the Source gamut or device
or image never comes into consideration. On the face of it, this idea has
the merit of insuring "blind" exchange and promotes a real modular color
processing which I believe is the cornerstone of the ICC system.
> whereas, ideally, superior results would come from
> a compression procedure established *at conversion time* to tailor the
> destination space for each given source image's gamut.
Now, how is that operationalized?
> (Does this mean
> conversion techniques that better respond to source image characteristics
> such as "low-key", or lack of very dark or light colors?)
I think it has the potential of tuning the conversion to the characteristics
of the Source better, indeed, but beats me as to how that's done in
practice. Perhaps Graeme or some other generous soul could shed some light
on this for us mere color mortals? I'm all ears.
> Also, my understanding is that *the destination gamut itself*, say for a
> given paper/printer/ink combination or for a scanner, would *not* be
> dynamic, since I assume that a given device's color gamut is more or less a
> fixed entity, with possibly only minor variations.
I don't know. Is this defined anywhere in V4 specs?
> Marco Ugolini
Roger Breton | Laval, Canada | email@hidden
http://pages.infinit.net/graxx
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| >Re: ICC v4 (From: Marco Ugolini <email@hidden>) |