Re: [Printing-architecture] Bye-Bye colord - OR - Poll ICC profiles via IPP for soft proofing

Michael Sweet <[email protected]> Tue, 23 Aug 2022 07:23:18 -0400

Newsgroups	dev.linux.lists.printing-architecture
Message-ID	<[email protected]>

Till,

> On Aug 22, 2022, at 9:04 AM, Till Kamppeter <[email protected]> wrote:
> ...
> Does this mean that in a colord-free world we proceed as follows:
> 
> If the printer does not provide built-in, downloadable profiles via the "printer-icc-profiles" printer IPP attribute, we have to get the profiles separately from the manufacturer's web site (printer is not self-contained, not really actually "driverless" ...) and upload them to the printer using HTTP PUT and registering them with the Set-Printer-Attributes IPP operation, so that they are available for all users of this printer. Am I right? And, after the upload, will the newly uploaded profiles be listed in the "printer-icc-profiles" IPP attribute, so that every user knows which profiles are available?

No.

Most printers don't host ICC profiles and don't support HTTP PUT or Set-Printer-Attributes.

You need to still have a way to associate ICC profiles with a print queue (temporary or otherwise), assuming of course you want to offer soft proofing.

> Now, with profiles listed by the "printer-icc-profiles" printer IPP attribute, could the soft-proofing software simply download and use these profiles?

For the class of printers that supports it, yes.  But I'd treat this as a source of profiles that can be downloaded on demand and associated with the local queue (alongside any profiles the user has installed manually).

> In case of a legacy printer the Printer Application should be able to hold color profiles, ideally both in the Snap's static file system image for the profiles which come with the Printer Application and in the variable/state file system for user-added profiles. Ideally such functionality should get added to PAPPL.

Right now I have no plans to add explicit support for ICC profiles to PAPPL as the class of printer being supported won't get anything out of it - *no* open source driver provides ICC profiles at this time, label and B&W laser printers won't benefit, and Gutenprint's notion of color management makes using ICC profiles basically useless - too many knobs.

(FWIW, PAPPL *does* know about ICC resource files and will assign the correct MIME media type for them, there just isn't a way to associate a profile with a Printer or the Job Template options that will select it...)

________________________
Michael Sweet

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