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TheStoneFox
TheStoneFox

Reputation: 3057

Convert PDF to PS in Ghostscript and preserve CMYK split

I have an RGB PDF which I've preflighted in Adobe Acrobat pro to a PDF x1a compliant PDF in US Web Coated SWOP v2.

The PDF now has 4 plates (C/M/Y/K)

C plate is empty M plate has 100% of a red image Y plate has 100% of the same red image K plate has 100% of black text on page (text is not on any other plate)

I'm now trying to convert that PDF into a PS using ghostscript

I've tried:

gs -dNOPAUSE -dBATCH -sDEVICE=ps2write -sProcessColorModel=DeviceCMYK -sOutputFile=output.ps input.pdf

But then when I distill this PS back to a PDF the text is on all the plates and not just the K plate.

I've used this online tool: http://pdf.my-addr.com/free-online-pdf-to-ps-convert.php

To also do the conversion and the distilled version of the PS generated by that preserves the plate breakdown. They are also using Ghostscript to create the PS.

So I'm assuming there is some setting I am missing.

Does anyone know?

Update 1

Trying in pdftops too and again it is taking my K plate and spreading it across all CMYK plates.

What secret magic are they doing on that web site to preserve plates?!

Update 2

Only main difference I can see is I'm using

%%Creator: GPL Ghostscript 905 (pswrite)

and that website is using

%%Creator: GPL Ghostscript 871 (pswrite)

Could it be a version thing, or are they doing something I'm not?

Upvotes: 3

Views: 2257

Answers (1)

KenS
KenS

Reputation: 31141

Ghostscript 9 and above use much better colour management than previous versions, but you have to get the ICC profiles correct. I'd guess you are using the default profiles and I think the first thing I'd suggest is that you use the current version of Ghostscript which is 9.07, I think there were a few changes made to the default profiles.

Its also possible that the PDF file now has an input RGB profile associated with it, which Ghostscript is now using whereas previously it didn't. I'd need to see the file to be able to tell better what is going on, but I have a sneaky suspicion that your 'pre-flight' conversion is causing the problem. What happens if you use the original PDF file ?

I very much doubt if the PDF file actually contains CMYK colour components, I would imagine all that has happened is that different profiles have been inserted into the file that control the conversion from RGB to CIE and from CIE to CMYK.

In passing, don't use pswrite. Its a terrible low-level output that converts much of the content into images. It produces large PostScript that processes very slowly and doesn't scale well (ie if the printer is a different resolution). Use the ps2write device instead.

By the way, since you've already used Acrobat, why don't you just use 'Save As' PostScript from there ?

Upvotes: 2

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