Re: Apple vs Apple
Re: Apple vs Apple
- Subject: Re: Apple vs Apple
- From: Henrik Holmegaard <email@hidden>
- Date: Wed, 26 Sep 2001 08:48:09 +0200
Marcus Pettersson <email@hidden> wrote:
Whats the diffference between the two engines: Apple CMM and Apple Color
Sync. For me it seems like the same thing.
The ICC profile format is the same as the ColorSync 2.0 profile format.
ICC profiles aren't much use without basic OS level system services
including the ability to query a profile database, delete a profile
in the profile database and so forth.
Optionally the OS may provide calculation services through a
calculation module, or a CMM in acronymics. The job of the CMM is to
create a single LUT from the 'tags' (: blocks of numbers) presented
by applications that use ICC profiles, and with that LUT make the
color space conversions requested. The concept is that the OS level
ICC API has a default CMM built in, and may load third party CMMs as
extensions, if application software does not prefer to use its own
CMM. Thus the Apple ICC API (which is what ColorSync is) has the
Apple CMM built in, and the Windows ICC API (which is what Image
Color Management is) has the Heidelberg CMM built in.
Versions of ColorSync prior to 2.6 did not correctly assemble the
tags into an asymetric conversion (one tag or intent from RGB to CMYK
for separation and another from CMYK to RGB for soft-proofing or CMYK
to CMYK for proof-printing), but assembled the tags symmetrically for
the same conversion both ways, which mostly meant you got Perceptual
for separation and Perceptual for simulation (: soft-proofing and
proof-printing). Then you could try to change the default intent in
your printer profiles (which is where the asymmetric switch is done),
but it made life really cumbersome. All this is old hat here on the
List and in publications from color vendors.
In comparison users of ICM prior to version 2.0 were worse off
because the Kodak CMM built in at the time only supported
calculations with 8 grid points, if I remember rightly. Meaning that
you probably wouldn't want to use it for an RGB to CMYK separation,
let alone for a proof which I never tried.
Anyway, application software developers are not buying into the
concept of OS level ICC services to the extent that I for one would
like to see. Professional Mac OS color software comes with its own
internal CMM, Helios, Photoshop, iQueue, ProfileMaker, BESTColor,
Linocolor ...
Part of the reservation has to do with a concern that Apple
development efforts may not always be stringently focussed on the
high-end graphics market, and another part has to do I suppose with
general concerns which will tend to make it more convenient with
application level CMMs because it limits what each party is
responsible for making work. Maybe something like that ...
Hope some of the history lesson helps ... -:).