[Gimp-print-devel] Color Management for Better Prints

[Karl H. K. <kh...@kh...>]

.. finally! It took me a long time to come up with something
that might be usefull for others as well... 

I just finished my first very rough cut of a color manager plugin
for the Gimp. This plugin uses ICC profiles to make color adjustments
on images loaded into the application. At this time it can only
deal with RGB images, and there are several other limitations. It
can however be used to improve the "color correctness" of images
printed with the Print Plugin. I have not yet tested it with the
latest release of the dither code, but what I've seen with the
earlier versions looked pretty good.

The problem with this type of color correction is that you of course
need a profile for _YOUR_ setup. It's not possible (if you are not
a big corporation that can invest tons of money into comming up with
a pretty good generic profile) to create a profile that will work with
every stc740 or sp870 and any paper/ink combination you throw at it.

I am using a profile generator running in vmware/Win98 to create
my profiles. These profiles need to be redone everytime something
in the dithering changes (or if you modify your paper or even more
important the ink you are using). 

If I find some time next weekend I will generate profiles for the
stc740 and the sp870/1270 that can be downloaded. These will hopefully
give better results than no profiles at all.

If somebody has access to an older Version of Corel Draw (I think
they distributed this with version 7): This package comes with 
the Color Profile Wizard (or whatever name they used in v7). You
need a colorimeter or spectrometer to generate profiles in their
newer software. As far as I know the v7 was also able to use a
calibrated scanner to create profiles that are of course not as
good as the ones generated with a spectrometer, but they are still
good enough for an improvement in color quality. 

The software I'm using (www.wiziwyg.com) is also scanner based. The
actual software can be downloaded from the Internet, you just need their
version of the IT8 target to actually use it.

Unfortunately at this time there is no free software available to 
create printer profiles (anybody interested in writing something? :-)
Scanner profiles can be created under Linux using www.scarse.coloraid.de.

You can always just use the color manager to color correct scanned images
and then print them uncorrected using a set of options that is known to
create good print outs.

A 0.02 version of this software can be downloaded from
http://home.rochester.rr.com/specht/test/color_manager-0.02.tar.gz
It requires the Linux version of the LCMS library from www.lcms.coloraid.de
(Marti is in the process of creating the next release).

This approach could also be used to do the RGB->CMYK transformation in
the print plugin. I just have not yet found a good way of creating CMYK
profiles that could be used for this. Once I have some free time I'm
planning on just using a generic CMYK profile and see what the results
are. This would take care of all the problems related to this transformation
that were discussed the other day on the list.

So, does this sound interesting? I have not announced this to anybody else,
I would like to get some feedback from the people on this list first. It
is related to printing, and in the future I would like to see color
profiles supported in the print plugin.

Karl Heinz