[Openicc] LINUX, Gutenprint / CUPS / Color policies

[Michael Sweet]

Robert L Krawitz wrote:
> ...
> Except that it's very hard to pass arbitrarily complex data (ICC
> profiles or linearization curves) through CUPS to the driver.  So if
> someone puts a lot of effort into creating good linearization curves,
> it's going to be very hard to actually use them.

You want to pass arbitrarily large device profiles as job options.

CUPS supports IPP attributes with opaque data (bytes) and/or arrays
of data which are passed to the driver.  The maximum size of any
single value is 65535 bytes, and the maximum number of values in an
array is 2^31-1...

IPP attributes are encoded in text format when passed to the driver,
so an attribute might become a very long option string when passed
to the driver.

So, you *can* pass arbitrarily complex/large data through CUPS.

That said, expressing the availability of this kind of driver option
in a PPD file is not something we support, and I doubt we ever will
support it (at least through PPD files) - it just isn't practical
for users to enter very long strings of binary data.

>    > The key of transparent and professional colormanagement for
>    > printing is a printerdriver, which allows linearization and use
>    > of profiles according the media/driver-setting.
> 
>    Actually, no, that isn't the key.  The printer driver could be a
>    relatively dumb program that has no concept of color management and
>    just pushes bits around.
> 
> Yes, but if there's only an 8-bit data path between CUPS and the
> driver (as is the case right now) there is an to doing the color
> management in the driver: greater precision.

Sure, but you've already run into limitations with that approach,
namely the difficulty in passing parameters and the hardcoding of
profiles into the driver.

Also, CUPS, ESP Ghostscript, and MacOS X will all include 16-bit
support very soon, long before there is a "standard" defined here...

> ...
> basically agree to disagree.  Commercial RIP's aren't particularly
> simple when you really want to tune them, from what I understand.
> ...

My experience with commercial RIPs (mainly EFI stuff) is that they
don't provide knobs for tuning.  You pick resolution, media, and
CMYK emulation, and they do the rest.  Some provide options for
overall CMYK densities, but you can't pass in your own custom
profiles - they have to be applied by the application prior to
printing.

I'm not arguing that we duplicate or depend on this interface, but
understand that a lot of people use "dumb" CMYK-based workflows so
we still need to support that kind of usage...

-- 
______________________________________________________________________
Michael Sweet, Easy Software Products           mike at easysw dot com
Internet Printing and Publishing Software        http://www.easysw.com