Hi Sven,

On Sunday 20 July 2003 11:44 am, Sven Neumann wrote:

> The CVS version does include some naive RGB <-> CMYK conversion
> routines and it has a CMYK color selector. What is still missing is
> support for loading and saving CMYK files. I would like to add this
> capability to a couple of file plug-ins such as TIFF. This doesn't
> mean that GIMP could work in CMYK but at least it would allow you to
> select colors by their CMYK values and to convert to CMYK when saving.
> A couple of users have told me that this functionality would
> dramatically improve the usefulness of GIMP for them and since it's
> such a simple change, we decided to give it a try.

Sounds like a good start.  If you want to investigate better RGB <-> CMYK 
conversion, then the littlecms library is a good choice to do the heavy 
lifting; it can do accurate conversions between colour spaces defined by ICC 

A default conversion from sRGB to SWOP-Coated seems to be the combination most 
houses use when no "proper" profiles are available, and will generally give 
considerably better results than a [c,m,y]=1-[r,g,b] type algorithm...

> Could you send me (or the list) a copy of this plug-in? I am
> particularily interested in the CMYK loading and saving routines.

I've made it available for download from my website, at

As it stands it compiles and works under 1.2 (Linux and Win32 - I use it at 
work on a windowbox).  I've nearly got it working under 1.3 - it'll do the 
separations themselves - but my filename-building routines need an overhaul 
for glib-2.0; they currently segfault...

The plugin itself uses littlecms to do the hard work, and can either place the 
separated channels in individual grey layers, or solid colour layers in 
"darken only" mode, with the data in the layer masks.

The plugin can't yet load CMYK images, but it can save them...

All the best,
Alastair M. Robinson

You know, you have to be careful not to get yourself
locked into this open systems stuff.  -- IBM executive

Gimp-developer mailing list

Reply via email to