[Openicc] questions about cupsICC on remote CUPS servers

Jan-Peter Homann homann at colormanagement.de
Wed May 18 07:48:17 PDT 2011

Hello to all,
It would be fine, if somebody could answer my questions or comment my 
workflow ideas.

As I´m not a developer, my ideas or workflow recommendations  may have 
problems or pitfalls. But my goal is to bring the discussion in a 
direction to discuss workflow opportunities, which could be realized in 
near future with current available technologies.

Thanks an best regards

Am 17.05.11 16:57, schrieb Jan-Peter Homann:
> Hello all,
> Following the dicussions in the OpenICC list, i have the impression, 
> that a color managed print path with a remote CUPS server is somehow 
> more tricky to implement, than a local installation.
> see e.g. statements from Hal. V. Engel
> > There is no good reason to point cups clients at localhost if the spool
> > is actually on another box. lpoptions should specify the remote spool
> > as one's default printer in such cases. And with that, both the CUPS
> > API and http over port 631 should give direct access to the PPD.
> Direct access to the PPD is already supported and this makes it 
> possible to get a list of CUPS configure profiles (IE. CUPSICCProfile 
> entries). Oyranos apready does this. But on remote print servers there 
> is no way to retrieve one of these profiles for things like proofing. 
> HTTP over port 631 does not expose the profiles unless you create a 
> sym-link from the dirrectory that is visible using http and port 631 
> to the profiles directory. At best this is a hack but it would allow 
> us to create a "retrieve proofing profile" API for prototyping 
> purposes without too much effort so that how all of this works from a 
> user prespective could be tested.
> *****
> Reading such discussion I realize, that I need a deeper understanding 
> of some Aspects of CUPS based workflows. Hopefully somebody could 
> answer to my questions:
> 1) Dynamic updating of PPDs for a remote CUPS server
> Are there tools available, which allow to update automatically a PPD 
> representing a remote CUPS server ?
> The use case here would be the installation of new combinations of 
> ICC-profiles with assigned driver settings on the CUPS server with an 
> automatic update of the cupsICC entries in the PPD.
> 2) CUPS client pulling PPD from the remote CUPS server
> Are tools available, which allow a CUPS cleint to pull a PPD from the 
> remote CUPS server ?
> (The usecase here is, that the printing GUI for sending a print job 
> gets an update, which driver settings (media / resolution) are 
> available at the remote server.
> 3) Configuration of target profile in pdftoraster based on cupsICC
> As being not a developer, the following described workflow is may 
> uncorrect in terms, that i`m using, so please correct me, if I´m wrong:
> - An administrator for the remote CUPS server installes new printer 
> profiles with assigend driver settings
> - The PPD for the remote CUPS server gets an update for installed 
> driver settings and links between driver settings (media / resolution) 
> and server side printer profiles.
> - In the print chooser on client side (e.g. CPD) the media / 
> resolution settings extracted from the PPD are always representing the 
> settings and profiles on the server side.
> - The user chooses one of the media / resolution settings and sends 
> the print job to the CUPS server.
> - The CUPS server reads the media / resolution settings from the 
> printjob and selects the approbiate printer profile through cupsICC 
> match.
> - The selected printer profile will be automatically configured as 
> target-profile in server side pdftoraster (GhostScript)
> - Gutenprint reads also the media / resolution settings from the CUPS 
> datastream and uses the correct Gutenprint configuration to output the 
> rasterfile from pdftoraster
> - optional: (pdftoraster embedds the printerprofile into the 
> rasterfile for e.g. rastertogutenprint. Gutenprints extracts the 
> Gutenprint settings, which have been embedded into the printer profile 
> before.
> - Workflow for creating media /resolution settings for ICC-off in 
> pdftoraster
> - an existing media / resolution settings is duplicated with a new 
> naming for media "GlossyNoICC"
> - no cupsICC entry will be associated with this new setting
> - pdftoraster will not triggered via cupsICC with a printer profile 
> and creates the rasterfile for rastertogutenprint without any 
> ICC-transformation
> - gutenprints reads the media / resolution parameters from the cups 
> stream an outputs the raster file with the correct settings
> Is such a workflow possible ?
> If yes, is it correct, that such a workflow with a remote server could 
> also be used with a local CUPS installation ?
> Maybe this decribed workflow is version wich could be implemented more 
> or less with the available tools and minor improvements e.g. for CPD 
> to pull the PPD from the remote server:
> The goals to reach would be:
> - Make the installation of new printer profiles with assigend driver 
> setting easy on CUPS server
> - Avoid any possible mistakes with profile handling on the client side
> - Only very few improvements on CPD are necessary
> - compatible with existing DeviceRGB print spool formats
> - allows invisible sRGB->printer colormanagement for standard users
> - open for the professional users a path for creating printing paths 
> with disabled ICC transformation in pdftoraster
> - allow crowd profiling for for the open source printing community
> - use the same workflow both for local and remote CUPS server 
> installations
> Goals wich are not reached in this step
> - No preview possible, because profiles could not be pulled from CUPS 
> remote server
> - no link to local color management frameworks like Oyranos or g-c-m / 
> colord, because profiles could not be pulled from CUPS remote server
> Such goals could be implemented later, if pulling of profile from the 
> CUPS server is realized.
> ****
> Comments and corrections are welcome
> Jan-Peter

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homann colormanagement --------- fon +49 30 611 075 18
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