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

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

Sven Neumann <neu...@un...> said: 

> Hi,
> 
> > 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.
> 
> could you explain the purpose of your plug-in in more detail? Usually
> you wouldn't want to do the color correction at the actual image data,
> but at the input/output level. So I would have guessed color correction
> belongs into the scanner software, the printer software and of course
> gimp's display routines. Support for the latter can be plugged into

Yes, yes and yes again. But because we don't have any CM support so far
I thoght that it's better to have a plugin that does some sort of 
color correction then to keep on hoping that somebody would come up
with an overall strategy for CM. 

> the GIMP using cdisplay modules. I'm wondering what purpose a plug-in 
> would have for serious work. But then having some working code is 
> definitely a good thing! 
 

Can you elaborate a little more about the cdisplay modules? This is the 
first time I'm hearing about these modules. Where can I find more 
information? 

At this time I'm doing the correction on the "live" data because it's
convenient. For the input part it's not a problem because you usually
want to work with the corrected scanned image anyway. The output part
is a bit weird: It's very interesting to see what the color correction
mechanism does to the image. It looks totally screwed on the screen but
printes just fine. In one of the next versions I'm planning on creating
a new image (a copy of the original) to do the output correction so that
the original one is not destroyed. 

There is one aspect of the output transformation for which it makes sense
to do it in a plugin: If you want to do soft proofing with a gamut check
then you have to display the result on the screen. This does not make sense
to do in the print module. One possibility is that the a soft proofing
plugin could query the print plugin about the profile to use and then 
work independently from the print module, or we could have some global
settings for color management that the Gimp application owns, but all the
other parts (input, output, soft proofing, ...) would just use this 
configuration information to find out which profiles to use, or ...

There are so many ways of doing this kind of work that it's probably not
up to me to decide which one to take. What I wanted to do is just put
something out that could be used as a basis for further experiments, but
still is useful for doing some real work.

Karl Heinz