[Openicc] explanations about Jan-Peters logical printer approach

[Jan-Peter Homann]

Hello list

There were some questions and interpretations about my concept for 
print-colormanagement with logical printers. I hope I can thinks more clear:


Writing a concept, which could be implemented durings some months
---------------------------------------------------------------
We should discuss concepts, which fitting the functionality of the 
applications we are talking about.
If colormanagement for the printing process should work for the normal 
user, we need a concept for delivering cannend profiles for standard 
print-settings.
We also need the possibility, that people can make their own set of 
profiles and printer-settings and make them easy downloadable and 
instalable for other users.
The concept of the logical printer is available in gutenprint, so I 
choosed it.
If somebody has an idea, which delivers the same functionality and which 
could implemented with actual solutions, please figure out:

- how to connect profiles and linearization-files with printer-settings ?
- How to make an easy and downloadble installer for a set of profiles, 
lin-files and printer-settings ?
- What has to do for realizing this concept, and who will do it ?


Dealing with the document-colorspace
-------------------------------------
If we make a color-transformation for printing, this is mainly a 
colortransformtion from the actual document-colorspace to the profile of 
the print-setting.
Ideal would be a mechanism, that gets the document-colorspace 
automaticly from the application from which is printed and the 
printer-profile from the print-setting, the user has chosen.
Unfortunatly, this seems not possible with actual applications.
So we have either configure the printer-profile in CUPS or configure the 
document colorspace in gutenprint (or another device-driver).

As most colormanagement-needs for the graphic arts professionals can 
solved with a handful of document-colorspaces:
- sRGB
- AdobeRGB
- SWOP
- ISOcoated
....
I choosed the solution to configure the document-colorspace in the 
logical-printer.
If we have solution to transport the document colorspace in the chain
- applications->CUPS->GhostScript->gutenprint, this would not necessary
But nobody in this list wrote, that there is a real way to do this.


The complicated linearization procedure
---------------------------------------
The linearization-procedure, which I have described, is the way, how 
inkjet profiling is done in high-end applications, and what is hardcoded 
in the standard-drivers for inkjets.

It didn´t mean, that the average user has to go this way to get 
nice-colors from his Inkjet.
This users should just use the preconfigured logical printers.
It would be also possible to make an UI, which e.g. manipulates the 
linearization curves of an logical printer with sliders (brightness, 
contrast, greybalance..)

Even is somebody want to make his own profile, he didn´t has to do the 
whole linearization procedure. He can take just take a given logical 
printer, prints his testchart with disabled colormanagement and enabled 
linearization and configure his onw profile in a duplication of this 
logical printer.
But if we want to target the high-end AND the massmarket, we need the 
possibility to make individual linearizations for each channel and set 
an Inklimit for the total amount off color BEFORE we print the testchart 
for profiling.



gutenprint as backend for CUPS/GhostScript, Gnomeprint, KDEprint, CAIRO
-----------------------------------------------------------------------
The concept is based on the input of a high-resolution bytemap with 8/16 
Bit color per channel in the document-colorspace.
So, this concept can be combined with all kinds of printerdriver/RIPs 
which can generate such bytemaps like e.g. CUPS/GhostScript, Gnomeprint, 
KDEprint or CAIRO.
The colortransformation from the document-colorspace to the 
printsetting-profile is always done in gutenprint.


Any questions ?
---------------
Please ask, if I´m not clear in my mails.

Greetings
:-) Jan-Peter















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homann colormanagement ------ fon/fax +49 30 611 075 18
Jan-Peter Homann ------------- mobile +49 171 54 70 358
Kastanienallee 71 ------- http://www.colormanagement.de
10435 Berlin --------- mailto:homann at colormanagement.de