[Openicc] GoSoC 2011: CPD and ... Mike Sweet workflow

Jan-Peter Homann homann at colormanagement.de
Fri May 13 08:46:06 PDT 2011

Comments inline

Am 13.05.11 16:35, schrieb Kai-Uwe Behrmann:
> Am 13.05.2011 07:09, schrieb Jan-Peter Homann:
>> 3) Do such use cases make it necessary to create PPDs ,where all color
>> related entries are stripped off, because the PPD concept is too
>> inflexible for the described use cases ?
>> Jan-Peter:
>> Yes, there is no more need for color related options in the PPD file.
>> The necessary informations for e.g. rastertogutenprint or
>> rastertovendorXY are just read from the ICC-driversettings, which is
>> embedded into the rsaterfile send to rastertogutenprint or
>> rastertovendorXY
> How then to create new calibrations? They would require colour options
> to be setable and not stripped away.
If we talk about calibration, we firstly have to define the meaning. In 
general, calibration bring a defined printer media combination to 
reference state, which allow the usage of standard printer profile for 
this reference stage.
In most cases, calibration is performed through manipulating the per 
channel LUTs of a printing device.

in workflows, where printer profiles are assigend to driver settings we 
have e.g. following possibilities:

1) "ICC-driversetting" contains calibration targets
The calibration targets are part of metadadate embedded in the printer 
profile (ICC-driversetting)
For doing a printer calibration, the user acticavates printer profile, 
for the standard he wants to calibrate the printer. The calibration 
software prints the calibration targets with driver settings extracted 
from the metadata of the ICC-driversetting. Than printed calibration 
target is read with a spectrophotometer and the calibration software 
extracts the the calibration target data from the metadata of the 
ICC-driver setting. The calibration software calculates the compensation 
curves for the calibration and write it bacj in the ICC-driversetting.
In the print workflow, the ICC-driversetting is embedded in the 
rasterfile for "rastertovendorXY"
rastertovendorXY extracts the general driver settings (screening, per 
channel limit... as also the current calibration curves)

2) Calibration is part of the printing software
The management of calibration targets is done inside the printing 
software as also the calculation and application of the compnesation 
curves to reach, the calibration target.
This is quite typical for highend sever based printing software. In this 
case the canned profiles for media / calibration standard are delivered 
to printing clients if colormatching or preview should be performed on 
the client side.
>> 4) What are the roles of Colormanagement Frameworks like e.g. Oyranos
>> or g-c-m / colord when it comes to the creation, exchange, download
>> and GUI representation of printing presets with assigned ICC-profiles ?
>> Jan-Peter:
>> So far as I now, both Oyranos and g-c-m / colord have till today not
>> published a concept for a direct interface to the printing GUI
>> concerning media and color options. (Please correct me, if I´m wrong..)
> Hmm
> http://www.freedesktop.org/wiki/OpenIcc#PPDcolouring was proposed to
> mark colour options as is now supported by Gutenprint and used by the
> Oyranos CUPS module,
> the ICC meta tag, which among others I reviewed, It's part of the
> specification since a while and Oyranos makes extensive use of that
> since quite a while,
> http://www.oyranos.org/wiki/index.php?title=Device_Settings#Printing for
> architecture plans including usability constraints and schemes
> a GSoC project to distribute the ICC device profiles over the internet and
> an other one to integrate these concepts into CPD, both are mentored by me
> What else do you miss?

So far as I understand the mentioned documents, the Oyranos workflow is 
based on the PPDs describing the available settings for the printer.
In the printing GUI (e.g. CPD) the PPD is parsed and the aviailable 
options are presented to the end user.

Frm my experience, the PPD concept is a very static concept and it is 
very hard to implement a workflow, where the use can download and 
install ICC-printer profiles with assigned driver settings and sees the 
result instantly in the printing GUI (e.g. CPD)

>> We have to consider, that both Oyranos and g-c-m/colord are mainly
>> "color management per computer" concepts. Printing is often a "color
>> management in the network" process, where e.g.
> How does you come to this impression?
> I have always prefered existing standards and usage of the actual
> systems capabilities.
> For Xorg it means that by using Xatoms we preserve network transparency.
> For PDF printing by adhering to PDF/X3 we are in theory not bound to a
> single host.
> These decisions where specially considered to preserve network capabilities.

I currently see not a concept for Oyranos, if driver settings and 
printer profiles are updated on print server application, that this 
information can be routed to all Oaranos instances on clients for the 
print server.
>> printer-settings with assigned ICC-profiles ("ICC-driversettings") are
>> installed at the print server side and should be available to all
>> printing clients without the need for manual installation.
>> On the other hand, we have often the case, that print client and print
>> server are running only on one local machine.
>> For handling both use cases, I would recommend, that installation and
>> management of "ICC-driversettings" are made always at the print server
>> side.
> While that sounds at first not that bad, it brings a lot of requirements
> and makes that not easy except for vendor profiles.

If it works with vendor profiles / settings, it should work in the same 
way for profiles / setting which are installed later on the print server.

So far as I understand the IPP concepts from PWG, we already have a 
dafted standard how a print server commicates the installed profiles and 
settings to a client without the usage of a PPD.

>> The role of CPD is to create a GUI for the media and color options
>> build from "ICC-driversettings" available at the print server and to
>> connect to Oyaranos or g-c-m/colord for communicating the choosen
>> "ICC-driversetting.
> The server options are generated typically from the PPD. The local
> interaction is mainly for per user interaction and ICC settings.
I want to get rid of the PPDs for color and media settings, because I 
think they are not flexible enough

best regards

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