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Re: PDF to PDF (gs?): rich RGB black to plain K (CMYK) black?

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In article <6d0f8a6c-3430-4b2f-8852-
ddb0e772e4ac@v8g2000yqb.googlegroups.com>, sd@imi.aau.dk says...

 
> How to convert pdf to monochrome?... - http://www.groupsrv.com/computers/about669835.html
> >> Print the original .pdf to PostScript in a file, edit the PostScript,
> >> distill the edited PostScript back to a new .pdf. Â For the editing:
> >> save [get then put/def] the existing PostScript definition (probably
> >> builtin) of any operator that sets color (setcolor, setcmycolor,
> >> setrgbcolor, setgray, ...), then install a new definition that does
> >> whatever you want based on the actual arguments and the saved
> >> original definitions.
> 
> ... unfortunately, I do not understand the postscript language enough
> to understand this advice :)

I can do that for you, as can others here, but it would be helpful to 
see an example. Ideally a PDF and PostScript file of a single page file, 
passed through your workflow.

That was we can be more certain about what to do, and give you better 
advice on how to achieve waht you want.


> > You are still converting the RGB into CMYK, if the
> > undercolorremoval/blackgeneration doesn't convert equal values of RGB
> > into CMYK, then you get a CMY output. It doesn't really matter which PDF
> > interpreter does this.
> >
> 
> Yes - but I was hoping, that if I 'properly' use color profiles
> (whatever 'properly' is), I could sort of have this conversion go "the
> right way" in this case: i.e. if it encounters R = G = B (grayscale);
> then treat it as K:100 CMY:0...

You only get CMYK output if you have an interpreter which applies the 
ICC (via a Colour Management System) profile to create CMYK. In general 
you won't get this. 

What usually happens is that you get a PDF which contains colours in an 
ICCBased colour space. Which your print shop probably won't like either.

Or possibly the colours still specified in RGB, but an OutputProfile 
attached, which simply describes the RGB space for which these were 
intended. A fully ICC ompliant workflow (ie including your printer) 
would be able to create a link from the ICC profile in the PDF to the 
ICC profile used for the printing device, and everything would magically 
work out. This is rare, it usually only works on closed workflows (that 
is, not accepting submissions from the outside world)

> > > So, I guess my questions can be summed up as:
> >
> > > * How can I convert a rich black text color in an RGB pdf - into a
> > > plain black text color in a CMYK pdf?
> >
> > There are a number of things you could try, but I would suggest either
> > printing to PostScript,
> 
> Ah - you actually meant something like choosing a .ps output (or
> "printing" to a .ps file) directly from OpenOffice? Yeah, that sounds
> like it should save a processing step...

Welk, I meant you could do that to get a PostScript file, which it might 
be easier to massage intot he form you want before converting it into 
PDF (assuming that's what your print shop wants as a submission).


> > Its also possible to set up an under colour removal function which
> > significantly affects how RGB is converted to CMYK (this is covered in
> > the PostScript Language Reference Manual).
> >
> 
> Thanks for noting this - I was somewhat aware that postscript language
> can also "process", but I am completely ignorant about its scope.

PostScript is a Turing-complete programming language. While there are 
thigns that are hard to do, very little is impossible.



> > If you can post a (small!) example file, preferably a single page, 
to
> > some publicly accessible URL I could take a look.
> >
> 
> Sure, here are the pdf's of the slides mentioned in the OP:
> 
> http://sdaaubckp.sf.net/post/img/blah-slide.pdf
> http://sdaaubckp.sf.net/post/img/blah-slideP.pdf
> 
> Many thanks for looking into this, :)

I'll go pull the files down now.


			Ken

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PDF to PDF (gs?): rich RGB black to plain K (CMYK) black? sdaau <sd@imi.aau.dk> - 2011-06-05 22:49 -0700
  Re: PDF to PDF (gs?): rich RGB black to plain K (CMYK) black? Matti Vuori <xmvuori@kolumbus.fi> - 2011-06-06 08:41 +0000
  Re: PDF to PDF (gs?): rich RGB black to plain K (CMYK) black? Helge Blischke <h.blischke@acm.org> - 2011-06-06 11:26 +0200
    Re: PDF to PDF (gs?): rich RGB black to plain K (CMYK) black? sdaau <sd@imi.aau.dk> - 2011-06-06 04:29 -0700
  Re: PDF to PDF (gs?): rich RGB black to plain K (CMYK) black? ken <ken@spamcop.net> - 2011-06-06 14:05 +0100
    Re: PDF to PDF (gs?): rich RGB black to plain K (CMYK) black? sdaau <sd@imi.aau.dk> - 2011-06-06 08:34 -0700
      Re: PDF to PDF (gs?): rich RGB black to plain K (CMYK) black? ken <ken@spamcop.net> - 2011-06-06 17:28 +0100
      Re: PDF to PDF (gs?): rich RGB black to plain K (CMYK) black? ken <ken@spamcop.net> - 2011-06-07 10:21 +0100
        Re: PDF to PDF (gs?): rich RGB black to plain K (CMYK) black? sdaau <sd@imi.aau.dk> - 2011-06-09 05:28 -0700
          Re: PDF to PDF (gs?): rich RGB black to plain K (CMYK) black? ken <ken@spamcop.net> - 2011-06-09 14:00 +0100
            Re: PDF to PDF (gs?): rich RGB black to plain K (CMYK) black? sdaau <sd@imi.aau.dk> - 2011-06-09 06:48 -0700
              Re: PDF to PDF (gs?): rich RGB black to plain K (CMYK) black? ken <ken@spamcop.net> - 2011-06-09 16:06 +0100
          Re: PDF to PDF (gs?): rich RGB black to plain K (CMYK) black? tlvp <mPiOsUcB.EtLlLvEp@att.net> - 2011-09-16 18:33 -0400
    Re: PDF to PDF (gs?): rich RGB black to plain K (CMYK) black? sdaau <sd@imi.aau.dk> - 2011-06-06 09:17 -0700
      Re: PDF to PDF (gs?): rich RGB black to plain K (CMYK) black? Helge Blischke <h.blischke@acm.org> - 2011-06-06 19:30 +0200
        Re: PDF to PDF (gs?): rich RGB black to plain K (CMYK) black? ole.hoppe@gmail.com - 2012-01-25 06:40 -0800
          Re: PDF to PDF (gs?): rich RGB black to plain K (CMYK) black? Helge Blischke <h.blischke@acm.org> - 2012-01-25 16:09 +0100
            Re: PDF to PDF (gs?): rich RGB black to plain K (CMYK) black? ole.hoppe@gmail.com - 2012-01-26 06:41 -0800
              Re: PDF to PDF (gs?): rich RGB black to plain K (CMYK) black? Helge Blischke <h.blischke@acm.org> - 2012-01-26 21:07 +0100
              Re: PDF to PDF (gs?): rich RGB black to plain K (CMYK) black? ole.hoppe@gmail.com - 2012-01-26 12:57 -0800
            Re: PDF to PDF (gs?): rich RGB black to plain K (CMYK) black? ole.hoppe@gmail.com - 2012-01-26 12:58 -0800

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