Trouble changing RGB to CMYK

[sedmont]

Hi, 

I've not been able to make work a plug-in that converts Gimp RGB into CYMK.  I downloaded the plug in (in several forms), but can't seem to install it. Also, it looks like I have paths for Gimp 2.0 and Gimp 2.8 on my computer. Gimp 2.8 opens.

Steps Taken

1) the zip files I downloaded from the internet:  

separate+-0.5.8
separate+-0.5.9-alpha2
separate+-0.5.9-alpha3

(I downloaded all three because I kept trying one after the other, and none seemed to be installed or working.)

2) When nothing happened, I unzipped them. By itself, of course, that still didn't give Gimp the desired capability.

3) So I tried putting the resulting unzipped folders directly in both of these two folders:

This PC > OS(C: )> Users > Ed > .gimp-2.8 > plug-ins >

and

This PC > OS (C: ) > Program Files > GIMP 2 > lib > gimp > 2.0 > plug-ins

4) I also went into Gimp and once there I went to 

Edit > Preferences > Folders > Plug-ins

There, under "Plug-in Folders" I saw:

C:\Users\Ed\.gimp-2.8\plug-ins 
and 
C:\Program Files\GIMP 2\lib\gimp\2.0\plug-ins

5) To those two lines, I added two further lines under "Plug-in Folders":

C:\Users\Ed\.gimp-2.8\plug-ins\separate+-0.5.9-alpha2
C:\Users\Ed\.gimp-2.8\plug-ins\separate+-0.5.9-alpha3

6) To check if that would do it, I closed Gimp and reopened it, then opened an image, then right-clicked, and on the right click menu I clicked on "Image" -- but the list of options still did not include "separate" ("separate" is apparently the option that lets you convert RGB to CMYK)

7) Next I tried opening the following folder (the folder unzipped from one of the zip files) and copying all the files in it: 
C:\Users\Ed\.gimp-2.8\plug-ins\separate+-0.5.9-alpha3

Having copied all those files, I pasted them into these two folders:

C:\Users\Ed\.gimp-2.8\plug-ins 
C:\Program Files\GIMP 2\lib\gimp\2.0\plug-ins

Still did not find any option to convert RGB to CMYK on Gimp. 

---

If the above looks chaotic, I was trying internet directions one after the other, each time seeing if the direction would work. But all the directions seem to be abbreviated on the assumption that everyone knows what is left out.

Anyway, thank you very much for any assistance.

[rich2005]

(02-18-2018, 08:20 PM)sedmont Wrote: Hi, 

I've not been able to make work a plug-in that converts Gimp RGB into CYMK.  I downloaded the plug in (in several forms), but can't seem to install it.....snip.....

I have to keep this a little on the short side. Using my netbook and not all info is handy.

separate+ is old. Goes back to Gimp 2.4. Does work in Gimp 2.6 but for Gimp 2.8 needs a dll from 2.6

Remove everything installed  and use the files from below. 

A couple of years (or more) ago I bundled it all up for someone. 
It is on my mediafire account http://www.mediafire.com/download/azx5y5...tility.zip

A demo showing how to install https://youtu.be/oQ5655I-wrY (Win10 but the same for Win7)

and an even older one on usage http://www.youtube.com/watch?v=2rby7r771D4&hd=1

Have a look at those and come back with problems.

[sedmont]

Thanks very much, Rich2005, that worked for installment.

Is there any way to use Gimp to paint on the CMYK image? Compared to the RGB image, the CMYK image lost a lot of color subtlety (didn't just change the colors). I'm working with Gimp on an image of Franz Marc's painting of a horse, and the RGB version has many shades of color. But with the CMYK version it's like someone just threw a bucket of bright red paint on the horse and the many shades of red, pink, orange, shadow and light, are gone. 

If there is no way to use Gimp to paint on CMYK, is there a way to alter the conversion from RGB to CMYK so that, even if the colors change, at least the subtlety and variety of color is not so badly lost?

Thanks again very much for any further ideas...

[rich2005]

No real way with Gimp 2.8, and to be honest that old plugin has a limited life. It will take a re-write of the code to work in the next version (2.10).

Gimp is 100% RGB, so while separate+ can open a CMYK tif and export a CMYK tif/jpeg, any editing is in RGB. Its use is as a final export when a printing company requires CMYK.

Many now accept RGB images so it is worth checking. Large photographic prints using colour laser printers produce great results although they expensive.

Quote:..is there a way to alter the conversion from RGB to CMYK so that, even if the colors change, at least the subtlety and variety of color is not so badly lost?..

If you look up RGB versus CMYK gamut you might get some information such as the first couple of pages here:
https://support.dma.ucla.edu/help/tutori..._guide.pdf
That shows the range of available colours for printed work is that much smaller, so some colours typically bright colours, are not available.


For CMYK it is best to start as you mean to finish. Apart from expensive editing applications, the free one to go for is Krita. https://krita.org

Your work in Gimp is not lost. Krita can open a RGB image and convert to CMYK (with the same restriction on gamut).

[sedmont]

Thanks for the excellent help. 
Does krita let you create images in CMYK and then work virtually on them in that form so that you can see on your computer screen what the hard copy print output will be?

[rich2005]

Quote:Does krita let you create images in CMYK and then work virtually on them in that form...

If you need CMYK rather than RGB you will certainly be better off painting in Krita using CMYK as the colorspace rather than Gimp RGB then converting....but...

Quote:...so that you can see on your computer screen what the hard copy print output will be?

Never going to be exact, your monitor is RGB.

You get better results if the monitor is calibrated but that is mainly photography biased. A good site for information is http://www.cambridgeincolour.com and start off in
https://www.cambridgeincolour.com/color-...inting.htm

A simple start for anything is the section on Monitor Calibration and Adjusting Brightness and Contrast most people have their monitor way too bright and are disappointed with dark prints.

For CMYK, this is hard going but lots of useful links.
http://www.northlight-images.co.uk/why-d...my-screen/

A lot depends on purpose, CMYK is often associated with big print runs, posters, flyers etc. If that is the case ask the printing company for a test print before ordering 1000's. The other one is TeeShirt prints etc. These are never going to be wonderful, you have to compromise.

If it is a one-off, back to: Does it need to be CMYK will the printing company accept RGB.

[sedmont]

Rich, thanks so much for all your excellent help. 
It looks like a fair amount of technical knowledge is required to be able even to approximately judge how and to what extent a printout will vary from what I see on my screen.  I now have Krita but can't seem to paint with it, at least not on a CMYK file. Anyway, I will have to come back to this and try again another time...You certainly got me as far as possible given my lack of knowledge of all this stuff. Thanks again!