Re: Dummy profile
Re: Dummy profile
- Subject: Re: Dummy profile
- From: Graeme Gill <email@hidden>
- Date: Fri, 13 Feb 2004 11:57:35 +1100
- Organization: Color Technology Systems
Jouni Mustonen wrote:
I was wondering if it is possible to create "dummy" ICC profile that doesn't
do anything?
Sounds stupid, but I suspect that one rip (no names here) doesn't allow me
to switch off output profile and that way it affects my target when printed.
Sort of, but probably not what you want. You can create real dummy profiles
only for abstract (PCS->PCS) or device link (Dev->Dev) profiles. These are
not the types of profiles people are normally dealing with. Most
profiles floating about the place are device characterization profiles
(Dev->PCS or PCS->Dev), which are used in pairs (Src and Destination
profiles) to transform from one device colorspace to another.
For a 3 channel device (ie. RGB or CMY), it is possible to create a
complementary pair of device profiles, in which gives an overall RGB->RGB
that doesn't alter the RGN values greatly. In theory, any RGB profile could
be used with itself for this, (ie. sRGB), and in some systems (like Colorsync),
the system notices that the src and destination profiles are the same
and skips the color transformation, guaranteeing a null transform.
When in comes to CMYK, then this isn't possible in any straightforward
manner, since you can't squeeze 4 channels (CMYK) into 3 (PCS) without
loosing information, so there's no way of creating a single pair of
profiles that tricks a system into reproducing CMYK without any alteration.
(I understand that Colorsync is an exception, and that it skips
the color transform even when the profile pair is the same and CMYK).
It is theoretically possible to work around this limitation with a series
of carefully crafter profiles, in concert with a series of test charts
(ie. use a separate profile and test chart for each black level you
want to test), but this is rather a hard road.
In reality, it's actually unlikely that any printing system that uses
ICC profiles has no way of printing a test chart in the device space. There
must be some such capability at some level, in order to create the ICC
profiles it comes supplied with. It is possible of course, that the
facility to do this is not made available to the end customer.
[ On our RIPs for instance, the Postscript CMYK device space is supported,
and it is easy enough to configure a "device link" CMYK->CMYK null profile
either manually, or by including some magic comments in the Postscript.]
Graeme Gill.
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