jaims put this on the wishlist:
There goes my wish
I have a couple of colleagues that work as artists/drawers.
They are using photoshop -among other sw- on a regular basis, but both would like to swap to a cheaper/non proprietary tool.
I’ve been talking to them about the gimp -and meetthegimp.org of course, which both of them love :-)- but seems like they are missing some stuff they need on a draw tool. Therefore, I’m not talking here of using the Gimp as a photo editing tool, mind you.
The number one issue for one of them is the CMYK stuff. He says he needs to be able to convert the color map from RGB to CMYK.
I told him I’d be investigating that point.
And, to start with, Gimp happens not to support CMYK natively. But I’ve found that there are several plugins that can be helpful with it: lcms, separate and separate+. But I haven’t been able to use them to generate a jpg file based on cmyk (my colleague sent me 2 jpg’s, the normal one and the cmyk-ed one).
And then, I don’t know if this stuff is also meaningful to us, people that use gimp for photo editing; I think that maybe would be in case of printing pictures to paper.
Rolf, if you find that interesting or you have already fought your way through the cmyk issues, I think it’d be nice to make a show on it. Drawer folks and cmyk issues is just another way of meeting the gimp after all 
Saludos
What I know about that fits on a postcard. Let me try to explain that far.
Let me start with the safe part - your CRT or LCD you are looking at. It uses an additive colour model and adds red, blue and green light in equal parts to get a perfect white background. The black letters are dark - they emit no light. This is the RGB model Gimp uses.
Printing uses a subtractive colour model and combines all colours out of cyan, magenta, yellow and black, also called “key”. Subtractive, because you take some parts of the spectrum away from the light that would reflect from white paper. If you print this text on perfectly white paper, all the light that falls between the letters will be reflected and all the light that hits the letters will be absorbed by the ink.
Black absorbs all parts of the spectrum in an equal amount. You can print with it a gradient from light gray (tiny drops with wide spaces between them) until solid black. But what is with red?
For red you have to absorb green and blue. Yellow absorbs green, magenta blue. So a red letter on a printout would be printed with tiny magenta and yellow ink drops. Cyan absorbs red - and when you add some cyan, you get a darker red.
But here are two problems. Real world CMY inks don’t add up to black - you get a muddy brown. And the coloured inks are way more expensive than the black ones. So instead of adding 10 cyan to get a darker red you would reduce yellow and magenta by 10 and add 10 black.
This “colour separation” seems not to be as easy as it sounds. Gimp can separate (Colours/Components/Decompose and look for CMYK) and even store CMYK TIFF files with a plugin. But the print people want to do more - I have no idea what.
Is there somebody out there with a clue about this stuff? Someone who can do a video? Or talk to me in an interview?
