[Scribus] CMYK - one last try

[David Purton]

No replies? Come on folks - at least some of you downloaded the eps.

Not even a "This is a limitation of Scribus currently, it is anticipated
it will be fixed in the future" or a "You blockhead, you've confused,
this, this and this, this is what you should be doing!" or even a "Gee I
see why you think Scribus is behavng inconsistently, but I don't get it
either." or "Yes Scribus is behaving oddly - go write a patch if you
want it fixed!"

Scribus is a fantastic program and I'm keen to see it keep improving.
One of the reasons open source software does improve rapidly is there is
a community who's using the software, finding bugs, submitting patches
etc. The place for discussing if there are bugs is mailng lists like this
one.

True, not everyone's workflow is the same, but I'm not trying to do
anything that I can't do in any other publishing orientated application
- be it Photoshop or CorelDRAW.


cheers

dc


On Sat, Dec 04, 2004 at 02:35:02PM +1030, David Purton wrote:
> One last effort to try and understand what Scribus is doing, since I'm
> not convinced so far that people on this list have followed me :(
> 
> So here follows a *really* long explanation, complete with lots of great
> examples :) And I do eventually get to the point too.
> 
> 
> Grab this file:  http://marshwiggle.net/CMYK.eps
> 
> This is a simple eps with four rectangles each in a different process
> colour (C, M, Y, K). View it in a text editor if you like.
> 
> Now, convert it to pdf using this ghostscript command:
> 
>         ps2pdf -dEPSCrop -dProcessColorModel=/DeviceCMYK CMYK.eps
> 
> Don't leave out the ProcessColorModel option, otherwise ghostscript will
> convert this to RGB colour without using colour management.
> 
> Open it up in acroread 5, or 6 if you are cursed with using one of the
> lesser operating systems. The colours you will see are correct and match
> reasonably closely what you would get if you sent this eps to an offset
> press or a nice colour postcript laser printer. (Trust me on this one -
> I work for a publising company and we frequently produce two colour
> books with Process Cyan as the second colour. I know what is is supposed
> to look like.)
> 
> The problem is not with Little CMS, because it too can produce the
> colours I want. Try this:
> 
> First convert the eps to a CMYK tiff using ImageMagick:
> 
>         convert -colorspace CMYK CMYK.eps CMYK.tif
> 
> Use tiffinfo to confirm you have a tiff in CMYK colour space.
> 
> Now produce a proof in RGB colour space using Little CMS (Replace
> "CMYKProfile" with the path to a CMYK profile on your machine.):
> 
>         tifficc -i CMYKProfile CMYK.tif CMYK-proof.tif
> 
> This looks pretty similar to what acroread produces.
> 
> I want to see these colours on screen in Scribus.
> 
> 
> For comparison you can also produce a proof of an RGB tif using Little
> CMS directly:
> 
> First convert our original eps to and RGB tiff (without colour
> correction):
> 
>         convert -colorspace RGB CMYK.eps RGB.tif
> 
> Now use Little CMS to make a proof (again replace CMYKProfile with the
> path to a CMYK profile on your machine):
> 
>         tifficc -p CMYKProfile RGB.tif RGB-proof.tif
> 
> This looks like what Scribus is giving me with colour management turned
> on.
> 
> 
> 
> Now, open Scribus (with colour management enabled). Import CMYK.eps
> (this is one nice thing about Scribus - eps import is great).
> 
> If anyone has Scribus producing colours similar to acroread, then let me
> know what your settings are.
> 
> To me the colours look like RGB colours that have been converted to the
> nearest available colour in the CMYK colour space - like the
> RBG-proof.tif image produced above.
> 
> But Scribus does seem to be at least partially treating them as CMYK
> colours, because if you print separations from Scribus, you will get one
> black square on each of your four pages. (Whether you have "Apply ICC
> Profiles" selected in the advanced printing options or not does not seem
> to make any difference.)
> 
> To me this is completely inconsistent. Either a colour is RGB or it is
> CMYK, not both at the same time. If Scribus is treating these four
> colours as RGB, then the separations that it is producing are incorrect
> (Open up RGB.tif which you created above in the GIMP and use the
> separate plugin to produce the correct separations).  If Scribus is
> treating these four colours as CMYK, then the on screen display is
> incorrect.
> 
> 
> So has this made any sense to anyone? Can anyone understand why I'm
> confused about colour management in Scribus?
> 
> 
> cheers
> 
> dc
> 
> 


-- 
David Purton
dcpurton at chariot.net.au
 
For the eyes of the LORD range throughout the earth to
strengthen those whose hearts are fully committed to him.
                                 2 Chronicles 16:9a
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