[Openicc] What is exactly needed for color management ... driver setup PPD

Richard Hughes hughsient at gmail.com
Tue May 31 13:44:27 PDT 2011

On 31 May 2011 21:13, Jan-Peter Homann <homann at colormanagement.de> wrote:
> Is it correct, that you are using the cupsICC qualifier specified in the PPD
> of the printer, for doing the described match of printer profile and driver
> setting ?

Correct -- See http://colord.hughsie.com/faq.html#qualifiers

> this leads for me for more questions:
> - Is it possible to prepare a printer profile, that it will automatically
> match the corrects cupsICC qualifiers for a given printer ?

Yes, although we haven't actually sat down and defined a DICT key and
value format that can be used in colord and oyranos. I suppose it
could be something like:

KEY:  "QUALIFIER_defaults"
VALUE: "RGB.Glossy.*,RGB.Plain.*"

KEY:  "COLORD_objectid"
VALUE: "cups-Photosmart-B109a-m"

But better ideas certainly welcome.

> - you you please describe step by step the enduser perspective, how a
> printer profile is configured in g-c-m, colord to match the cupsICC
> qualifiers for a given PPD ?

Ohh, I think most of it should be automatic. In gcm-calibrate which
actually creates the ICC profile using argyllcms we should add the
extra DICT metadata to the argyllcms-generated profile to make this
possible. In the GTK print dialog in the calibration tool we know
exactly the resolution and paper type at calibration time so we can
fill these in directly without asking the user.

For the "downloaded profile from the internet" use case I agree we
need some extra UI, and this is also where the meta-profile concept
comes in handy, that-is that colord profiles are abstracted from the
file profiles themselves and we can store additional metadata
persistently on the meta-profile that isn't actually in the dict tag.

As to what the UI would look like I'm not sure. I suppose it would be
some kind of modal dialog like:

Use this profile when printing:

[x] on glossy paper
[ ] on plain paper
[x] when draft mode


Or something like that. This would be buried in the control center
panel, not in the print dialog or the CPD; this is a system setting
and is not per-job.

> (Or is it needed to prepare the PPD in advance, so that the the match of
> cupsICC qualifiers is encoded into the PPD ?)

Nahh, I'm treating the PPD as read-only in my design.

> Rendering Intents:
> How do you handle the rendering intent from target colorspace (e.g. sRGB) to
> the printer profile, if the PDF spool file is DeviceRGB ?

I'm not sure I understand the question. I'm assuming the pdf/ps file
when it gets to the gstoraster stage has some kind of information
about the rendering intent to use for each object. There's certainly
nothing we can use as a heuristic reliably, and this will be a
per-application or even per-document setting.


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