[Openicc] CPD Color Management prototype (GSoC '11)

[Hal V. Engel]

On Tuesday, August 16, 2011 08:58:54 AM Till Kamppeter wrote:
> On 08/15/2011 07:03 AM, Joseph Simon wrote:
> > Hello Till.
> > 
> > I am very close to hammering down the final nail on the
> > profile-selection code for the color-managed CPD prototype. However,
> > in order to do so I would need to know this little detail about the
> > real CPD:
> > 
> > Are the options in the "ICC color profile" drop-down widget part of
> > the PPD file? ("auto assign", "set by application", etc.) Or can we
> > extract these options straight from the GUI?
> 
> AFAIK this option is supposed to list the color profiles available for
> the print queue (defined in the PPD) with an additional entry to not
> choose any of the profiles and choosing a profile should set the options
> related to it appropriately.
> 
> Color management people, am I right?
> 
>     Till

I think Joe is talking about how the CPD goes about either selecting a 
"default" profile or having the user or the app that called the CPD decide what 
profile to use.

Auto Assign:

"Auto Assign" will defer to the system to select the profile and the user can 
only influence this by changing print related setting (media, resolution...).  
This means using either what is configured in the PPD or what is supplied by 
Oyranos.  It might go something like:

If Oyranos is available the CPD will ask Oyranos what profile to use.  Oyranos 
will have logic to decide if using the PPD supplied profiles is correct either 
because the user/printer admin has not configured any additional profiles or 
none of the externally configured profiles are correct for the media/color 
mode/resolution...

If Oyranos is not available then the the CPD will use whatever profile is 
configured in the PPD that is the closest match to the current printer 
settings.  Actually CUPS should do this automatically if the correct filters 
are installed so in this case the CPD should just pass the spool file through 
to CUPS and let it handle profile selection.

This will be the default setting and most users will never use anything else.

Set by Application:

In this case the application requesting the print job will supply the printer 
profile as an explicit override.  Since we don't currently have any open source 
apps other than perhaps Scribus that are capable of setting this (IE. Scibus 
could conveivably set the output intent in it's generated PDFs) this will 
likely be rarely used.

User Selected:  (not sure if this is the terminology used)

This will allow the user to use a file dialog to select a local profile that is 
then embedded in the spool PDF as an output intent.  But it might also allow 
the user to select from a list of PPD and Oyranos supplied profiles.

Some observations.  

1. Currently most PPD files have broken cupsICCprofile settings.  These point to 
directories that do not exist and to profiles that are not installed on most 
machines other than Macs.  Until that is fixed most of this is at best difficult 
to test and more or less speculative in nature.

2. CUPS still does not make profiles available in a transparent way and this 
makes testing difficult since it requires that the system be tweaked to make 
this work.

4. In the above colord could be substituted for Oyranos but I think the 
currect CPD work is based on using Oyranos.  But the concepts should be the 
same for either Oyranos or colord.

5. The current CM CPD work is more in the nature of a prototype.  IE. it is a 
strawman intended to give us something to look at and play around with rather 
than a final definitive version.   There may be things there that are surprising 
or that take us in directions that we didn't expect (I don't know if this is 
the case since I have not seen what it looks like or how it works).  But it 
will give us something to work with moving forward and it shouldn't be too 
difficult to mold it into a more or less finalized state that fits our collective 
vision. 

Hal
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