[poppler] pdftops : issue with colorspaces with some printers (gray vs rgb)

[William Bader]

I could make a patch to add a -preservecolorspace option tonight if no one has any objections.
>I'm a java developer, not comfortable in C/C++... not sure I would be able to make a pull-request in git.
The command to get the poppler source is "git clone git://git.freedesktop.org/git/poppler/poppler" or download a stable release from http://poppler.freedesktop.org/ (The stable releases need less infrastructure to build than the git source.)  Patches can be posted to https://bugs.freedesktop.org
William
Date: Wed, 4 Feb 2015 18:05:03 +0100
Subject: Re: [poppler] pdftops : issue with colorspaces with some printers (gray vs rgb)
From: benjamin.lefevre at photobox.com
To: williambader at hotmail.com
CC: poppler at lists.freedesktop.org

Thank you William for your answer.
Actually I saw in the release notes ( http://poppler.freedesktop.org/releases.html ) what you mention. The 0.17.2 introduces the optimization you are talking about:poppler-0.17.2.tar.gz (Mon Aug 15, 2011):  PSOutputDev: Make level1sep, level2sep and level3sep write gray instead of rgb for gray images

Yes it makes a problem for me, and it would be great to have this feature. How can I proceed to have it?  I'm a java developer, not comfortable in C/C++... not sure I would be able to make a pull-request in git.

2015-02-04 17:44 GMT+01:00 William Bader <williambader at hotmail.com>:



I think that the cause is a patch that I submitted in May 2011 around the time of poppler 0.17.0.
Search for isGray in poppler/PSOutputDev.cc
I use pdftops to make postscript files that will be printed on a newpaper press.
My application was being sent PDFs with embedded logos that looked gray but were actually in RGB color space, and they were not getting separated correctly on color pages.
I added a check in PSOutputDev that if every pixel of a RGB bitmap was equal R, G, B, it will be written as a grayscale bitmap, which fixed my separation problems and made the files smaller.
If that makes a problem for you, it should be possible to add a command line option to control the RGB to grayscale conversion, maybe similar to some of the distiller options in ghostscript http://ghostscript.com/doc/current/Ps2pdf.htm
William

Date: Wed, 4 Feb 2015 16:18:59 +0100
From: benjamin.lefevre at photobox.com
To: poppler at lists.freedesktop.org
Subject: [poppler] pdftops : issue with colorspaces with some printers (gray	vs rgb)

Hi everyone,
My name is Benjamin and I am french.
I'm new on this mailing list :)
 I come to you for a question or maybe for a feature request (at this stage, I'm not sure).
Please look at this pdf (dropbox: https://www.dropbox.com/s/yoj6h3o4irnlgun/source.pdf?dl=0 )
There are two monochrome images (in DeviceRGB in the pdf).
After executing 'pdftops', the images are cut in half, with the top part in DeviceRGB and the bottom in DeviceGray. This causes colorimetric issues on some of my printers (most of them in fact).
Is it possible to preserve DeviceRGB by executing pdftops? I did not manage to achieve it with the few available options provided by pdftops.....
Or would it be possible to have a new option in poppler (pdftops in my case) to preserve colorspaces, and to not optimize the monochrome images in DeviceGray? 
Thank you in advance,
Benjamin.








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Benjamin Lefevre      Senior
Software Engineer / iWays & iRender

Email                          benjamin.lefevre at photobox.com

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