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

Michael Sweet <[email protected]> Wed, 24 Aug 2022 16:00:32 -0400

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

Sebastien,

> On Aug 24, 2022, at 11:47 AM, Sebastian Wick <[email protected]> wrote:
> ...
> For input they all support sRGB, sGray. Some also support AdobeRGB, but
> how do you know when a printer supports AdobeRGB? Some support device
> profiles and they are advertised with printer-icc-profiles.

The "pwg-raster-document-types-supported" and "urf-supported" attributes advertise the supported raster color spaces. We use that to determine which cupsColorSpace values to use in the PPD file.

> Assuming I know what input profiles the printer supports, how do I tell
> the printer what profile my document is in? You already partially
> answered the question: PDF printers use the embedded ICC profiles. Do
> all the document formats support embedded profiles? Is that always how
> printers figure out the source profile of a document?

PDF supports it, PostScript somewhat less so.  For raster (image/pwg-raster and image/urf), the color space is a single well-known space (sRGB, sGray, AdobeRGB) or device color space (RGB, CMY, CMYK, K, W), for which the Client has converted all color data in the source document to the destination color space.

>>> Is this kind of information documented somewhere?
>> Yes, in the IPP Everywhere specification:
>> 	https://www.pwg.org/ipp/everywhere.html
> 
> Either I missed something, which is highly likely, or the way color
> management is supposed to work is very open to interpretation (looked at
> IPP Everywhere v1.1, and PWG 5100.13).

We are adding clarifications to the updates of these documents now, so if you can provide some specific feedback I can make sure your concerns are addressed.

________________________
Michael Sweet

signature.asc (application/pgp-signature, 833 B)