[pdftex] color-separation with PDFTex

Michael Chapman pdftex at mchapman.com
Tue Aug 30 03:34:00 CEST 2005

On Sunday 28 August 2005 6:16 pm, Andreas Demant wrote:
> Hi,
> is it possible to generate color-seperated PDF's?
> I want a black PDF and a color-PDF without black, so i could print the
> black version on a normal laser-printer and only the colors with a
> colorlaser.

Sorry, Andreas, this is more a sympathetic than a helpful reply ....

We have the same need and not just for DTP. Our printers use classic offset 
machines, but have to send off PDFs for colour separation for quadrichrome 
(CMYK) separation .... which is time consuming.

For two colour printing we often do a 'cheat' separation in-house. (Two 
colour is usually black and a spot colour.)
 - Text can be flipped in and out using (in Latex) \textcolour{COLOUR}{the 
wanted/unwanted text}
(Also there are the Tex 'phantom' commands, but I never got that far ...)
 - For images we resorted to making an 'empty' image file of the same size. 
(I did consider Latex 'draft' mode which nicely removes the images, but 
leaves a box and the image name -there must be some way of 'printing' those 
in white, but I took the easy if tedious way out ....).

Then you have two PDF files, one for each colour. (The Latex 'crop' package 
will give you nice alignment marks.)
(Actually we wanted three files. The two seperated colours, each in black on 
white for making the films, and one with both colours to print out 
drafts/proofs for pre-submission approval, on a small colour laser. The whole 
business is ripe for 'automation', but thus far it's only once every several 
months ...)

One could extend this to full colour separation, but it would be tedious.
Also previous discussion on this list has commented on the problems of 
conversion of RGB images to CMYK .....

Hope someone else can be of more help ....


BTW Trying to 'register' your two colour runs may well be problematic.
We even have problem getting B&W laser printers to _roughly_ put text on a 
consistent place when doing two-sided printing.
A friend with a large printing business wanted to do small print run 
perfectly aligned two-sided laser printing. Tells me he hasn't got a quote 
under 500,000 yet ...

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