[Openicc] Is CUPS the right place for printer color management...

[edmund ronald]

On Mon, Feb 7, 2011 at 10:00 PM, Chris Murphy <lists at colorremedies.com> wrote:
>

> Ask who is going to build the drivers before something else gets
> implemented. Gutenprint does leverage *cupsICCProfile, although just as
> defaults for grayscale, RGB and CMYK.

As I understand things, at the moment we tell Mac OS X that we accept
its standard handoff workspace (previously Generic RGB) and we have
Robert's manually constructed behavior that prints files in this
workspace fairly decently. In the future the printers should be
profiled for "standard" media, and FOR CONSUMER DEFAULTS we would
somehow invoke a conversion from  the handoff space by using the
printer profile. On OS X I think we will be able to continue to
persuade the OS to do the conversion automagically, in Linux we might
have some special piece of code to do that if we have to - but this is
just so we have nice consumer default behavior.

At the moment, because of the desire to have decent default behaviors,
the default print settings for Gutenprint do not really exercise a
modern printer's gamut; this should change in the future, as soon as
profile conversion can be invoked to render the handoff space data.

Concerning non-default behavior, for "pro" and "prosumer" printing the
model I envision is that  the user does profiled printing, via a
profile, either RGB or CMYK. I don't think we will do any workspace
conversion, it's up to the user to apply a profile to his data
somewhere upstream; we don't have the smarts to program the profile
application ourselves well enough. We will provide some usable
RGB=>CMYK conversion so that there is a usable RGB workflow.

I HAVE PERFORMED PRELIMINARY TESTING myself of this "pro" user-model,
using our existing RGB=CMYK conversion, and can affirm that results on
current Epson graphics printers will be roughly comparable to what is
achievable with the present vendor drivers in quality, although there
might be a very slight gamut advantage with the native Epson drivers.
Once we go this way -sometime in the future - we would expect to
supply "decent" canned profiles for this mode for the main Epson
media, and other media can be profiled by us or profiles can be
contributed by users TOGETHER WITH THE APPROPRIATE MEDIA SETTINGS.

Edmund



Edmund



> If the drivers are never going to automatically help the user pick a profile
> for a print condition, and there won't be some canned profiles for these
> conditions, then further use of *cupsICCProfile is indeed pointless.
> In any event, manual selection of an ICC profile (a custom one presumably)
> is something that's outside of the PPD, supplied in the print dialog by
> whatever generates that dialog (application? standard system dialog?) and
> that needs to be captured so the profile is included in the PDF print spool
> file.
> The conversion using that profile happens downstream by Ghostscript along
> with rasterization. Then CUPS moves the color managed raster file along to
> another filter for either display (maybe using a tiff filter) or to the
> printer.
>
>
> Chris Murphy
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