[XeTeX] Outputing PDFs in CMYK ColorSpace

[George N. White III]

On Tue, Jan 19, 2010 at 8:08 AM, Clinton Gormley <clint at traveljury.com> wrote:

> On Tue, 2010-01-19 at 03:57 -0800, Michiel Kamermans wrote:
>> Since plugins for Acrobat don't do much on *nix (unless you're running
>> things in wine, and let's not go there for production tool chains), you
>> may want to consider learning ghostscript, which was specifically
>> designed to manipulate postscript and pdf files - however, ghostscript
>> is rather unfriendly to people who "just want to do ... or ...", you
>> need to read the manual and become familiar with the too. It's a pretty
>> challenging learning curve, but figure out how to properly use it and
>> CMYK conversion should be a breeze.
>
> Thanks Michiel - you've given me hope (albeit tinged with trepidation :)

CMYK conversion of arbitrary images is an unsolved problem.
See: <http://www.printingforless.com/rgb-cmyk.html>, who advise
authors to provide CMYK themselves, and give some advice on how
to do that.

Images are created on systems with no color controls, typically using RGB
which has a different gamut.  I work in remote sensing where people tweak
images to bring out some feature of interest in their personal system, only
to find the feature is not visible in print.    Even if you do the
conversion on
an image and send the PDF to  the author for approval you can't control the
author's viewing environment, so you end up with:

author: the PDF is cXXp, fix it
you: how about this?
author: still cXXp
[many interations]
author: well, if that is the best you can do
you: release to printer
author: the printed version is unacceptable.

Maybe you could send the author a PDF with a layout of a dozen images
using different conversions and suggest they print it and also view on multiple
systems and choose the one that works best overall.

In my experience, Adobe tools do RGB to CMYK much better than simple
conversions using, e.g., the Redbook formula.  See examples at:

<http://designer-info.com/DTP/rgb_to_cmyk.htm>

-- 
George N. White III <aa056 at chebucto.ns.ca>
Head of St. Margarets Bay, Nova Scotia