Converting PDF to CMYK (with identify recognizing CMYK)
Ok, here is something, at least...
Originally, I need this as a way to make sure that my PDF files are in CMYK, and have the text as "plain black" C:0, M:0, Y:0, K:100 - since I've had problems with printers previously, where they would complain about my Latex PDFs containing "rich black" for text (which thus cost more). And I usually go for identify since it seems to be the only tool that can parse PDFs and colors (and it is also relatively easy to remember).
Well, I read through Tech Tip: Using Ghostscript to Convert and Combine Files | Linux Journal; where it is recommended to use the tiffsep device of gs to obtain separations. And this for me fulfills the same role as identify; I can just do:
$ gs -sDEVICE=tiffsep -dNOPAUSE -dBATCH -dSAFER -r150x150 -sOutputFile=p%08d.tif test.pdf
$ ls p*
p00000001.Black.tif p00000001.Magenta.tif p00000001.Yellow.tif p00000001.Cyan.tif p00000001.tif
$ eog p00000001.tif
... and then I can just 'iterate' through the separation images using left/right arrow - and it is immediately obvious if it is 'plain black' or 'rich black'.
So this shows that, regardless of what identify shows, the test.pdf from pdflatex actually has 'plain black' as text color, as it is supposed to (the other separations are blank) - however, doing something like:
# do a conversion of original PDF
$ gs -dPDFA -dBATCH -dNOPAUSE -dNOOUTERSAVE -dUseCIEColor -sProcessColorModel=DeviceCMYK -sDEVICE=pdfwrite -sOutputFile=out_pdfa.pdf test.pdf
# do a separation on the converted pdf
$ gs -sDEVICE=tiffsep -dNOPAUSE -dBATCH -dSAFER -r150x150 \
-dFirstPage=1 -dLastPage=1 -sOutputFile=p%08d.tif out_pdfa.pdf
# view
$ eog p00000001.tif
... will reveal that the particular out_pdfa.pdf actually has 'rich black' - i.e. ink for text goes over all four separations! (identify also shows this one as RGB, too).
So, I hope that this gs/tiffsep technique is more reliable than identify :)
Note: I'm using Ubuntu Natty, which ships GhostScript 9.01 - however, that one has a nasty bug with tiffsep: Bug 691857 – tiffsep crashes in Version 9 (missing lab.icc). That has been fixed for 9.02 - and 9.02 has been released as ghostscript in oneiric. To use 9.02 under Natty, I followed how to update a single package using apt-get? - Ubuntu Forums:
sudo nano /etc/apt/sources.list # add deb http://archive.ubuntu.com/ubuntu/ oneiric main restricted
sudo apt-get update
sudo apt-get install ghostscript # this upgrades only gs and dependencies
sudo nano /etc/apt/sources.list # remove/comment oneiric repo
sudo apt-get update && sudo apt-get upgrade # should be back to normal here
Note that with the buggy 9.01 version, even this command would fail:
$ GS_LIB=/usr/share/ghostscript/9.01/iccprofiles/ gs -sICCProfilesDir=/usr/share/ghostscript/9.01/iccprofiles/ -sDEVICE=tiffsep -dNOPAUSE -dBATCH -dSAFER -sOutputFile=p%08d.tif out_pdfa.pdf
...
sfopen: gs_parse_file_name failed.
sfopen: gs_parse_file_name failed.
... gsicc_open_search(): Could not find lab.icc ...
.. and with 9.02, there is no need to specify sICCProfilesDir explicitly.
sdaau, the command you used for trying to convert your PDF to CMYK was not correct. Try this one instead:
gs \
-o test-cmyk.pdf \
-sDEVICE=pdfwrite \
-sProcessColorModel=DeviceCMYK \
-sColorConversionStrategy=CMYK \
-sColorConversionStrategyForImages=CMYK \
test.pdf
Update
If color conversion does not work as desired and if you see a message like "Unable to convert color space to Gray, reverting strategy to LeaveColorUnchanged" then...
- your Ghostscript probably is a newer release from the 9.x version series, and
- your source PDF likely uses an embedded ICC color profile
In this case add -dOverrideICC to the command line and see if it changes the result as desired.
Update 2
To avoid JPEG artifacts appearing in the images (where there were none before), add:
-dEncodeColorImages=false
into the command line.
(This is true for almost all GS PDF->PDF processing, not just for this case. Because GS by default creates a completely new file with newly constructed objects and a new file structure when asked to produce PDF output -- it doesn't simply re-use the previous objects, as a more "dumb" PDF processor like pdftk does {pdftk has other advantages though, don't misunderstand my statement!}. GS applies JPEG compression by default -- look at the current Ps2pdf documentation and search for "ColorImageFilter" to learn about more details...)
I have an unrelated problem but I am also struggling with CMYK PDFs currently.
I wrote this little script here (it's called pdf2pdfx):
#!/bin/bash
gs \
-dPDFX \
-dBATCH \
-dNOPAUSE \
-dNOOUTERSAVE \
-sDEVICE=pdfwrite \
-sColorConversionStrategy=CMYK \
-dProcessColorModel=/DeviceCMYK \
-dPDFSETTINGS=/prepress \
-sOutputFile="${1%%.pdf}_X-3.pdf" \
PDFX_def.ps \
"$1"
and my PDFX_def.ps contains the following (I removed the ICC profile and defined FOGRA39, this should be OK):
%!
% $Id$
% This is a sample prefix file for creating a PDF/X-3 document.
% Feel free to modify entries marked with "Customize".
% This assumes an ICC profile to reside in the file (ISO Coated sb.icc),
% unless the user modifies the corresponding line below.
systemdict /ProcessColorModel known {
systemdict /ProcessColorModel get dup /DeviceGray ne exch /DeviceCMYK ne and
} {
true
} ifelse
{ (ERROR: ProcessColorModel must be /DeviceGray or DeviceCMYK.)=
/ProcessColorModel cvx /rangecheck signalerror
} if
% Define entries to the document Info dictionary :
% /ICCProfile (/usr/share/color/icc/ISOcoated_v2_300_eci.icc) def % Customize or remove.
[ /GTS_PDFXVersion (PDF/X-3:2002) % Must be so (the standard requires).
/Title (Title) % Customize.
/Trapped /False % Must be so (Ghostscript doesn't provide other).
/DOCINFO pdfmark
% Define an ICC profile :
currentdict /ICCProfile known {
[/_objdef {icc_PDFX} /type /stream /OBJ pdfmark
[{icc_PDFX} <</N systemdict /ProcessColorModel get /DeviceGray eq {1} {4} ifelse >> /PUT pdfmark
[{icc_PDFX} ICCProfile (r) file /PUT pdfmark
} if
% Define the output intent dictionary :
[/_objdef {OutputIntent_PDFX} /type /dict /OBJ pdfmark
[{OutputIntent_PDFX} <<
/Type /OutputIntent % Must be so (the standard requires).
/S /GTS_PDFX % Must be so (the standard requires).
/OutputCondition (Commercial and specialty printing) % Customize
/Info (none) % Customize
/OutputConditionIdentifier (FOGRA39) % Customize
/RegistryName (http://www.color.org) % Must be so (the standard requires).
currentdict /ICCProfile known {
/DestOutputProfile {icc_PDFX} % Must be so (see above).
} if
>> /PUT pdfmark
[{Catalog} <</OutputIntents [ {OutputIntent_PDFX} ]>> /PUT pdfmark
Identify then correctly reports CMYK colorspace. Before:
tbart@blackknight ~/orpheus/werbung/action $ identify -verbose action_schulungsvideo_v3_print.pdf
Image: action_schulungsvideo_v3_print.pdf
Format: PDF (Portable Document Format)
Class: DirectClass
Geometry: 612x859+0+0
Resolution: 72x72
Print size: 8.5x11.9306
Units: Undefined
Type: TrueColor
Endianess: Undefined
Colorspace: RGB
Depth: 16/8-bit
Channel depth:
red: 8-bit
green: 8-bit
blue: 8-bit
Channel statistics:
Red:
min: 0 (0)
max: 65535 (1)
mean: 53873.6 (0.822058)
standard deviation: 19276.7 (0.294144)
kurtosis: 1.854
skewness: -1.82565
Green:
min: 0 (0)
max: 65535 (1)
mean: 55385.6 (0.84513)
standard deviation: 19274.6 (0.294112)
kurtosis: 2.09868
skewness: -1.91651
Blue:
min: 0 (0)
max: 65535 (1)
mean: 51020 (0.778516)
standard deviation: 20077.7 (0.306367)
kurtosis: 0.860627
skewness: -1.52344
Image statistics:
Overall:
min: 0 (0)
max: 65535 (1)
mean: 53426.4 (0.815235)
standard deviation: 19546.7 (0.298263)
kurtosis: 1.59453
skewness: -1.75701
Rendering intent: Undefined
Interlace: None
Background color: white
Border color: rgb(223,223,223)
Matte color: grey74
Transparent color: black
Compose: Over
Page geometry: 612x859+0+0
Dispose: Undefined
Iterations: 0
Compression: Undefined
Orientation: Undefined
Properties:
date:create: 2011-09-14T15:38:57+02:00
date:modify: 2011-09-14T15:38:57+02:00
pdf:HiResBoundingBox: 612.283x858.898+0+0
pdf:Version: PDF-1.5
signature: 210bfc9cf90e3b9505385f8b2267da1665b5c2de28bb5223311afba01718bbeb
Artifacts:
verbose: true
Tainted: False
Filesize: 1.577MBB
Number pixels: 526KB
Pixels per second: 52.57MB
User time: 0.020u
Elapsed time: 0:01.009
Version: ImageMagick 6.6.5-6 2011-04-08 Q16 http://www.imagemagick.org
after:
tbart@blackknight ~/orpheus/werbung/action $ pdf2pdfx action_schulungsvideo_v3_print.pdf
GPL Ghostscript 9.04 (2011-08-05)
Copyright (C) 2011 Artifex Software, Inc. All rights reserved.
This software comes with NO WARRANTY: see the file PUBLIC for details.
Processing pages 1 through 1.
Page 1
tbart@blackknight ~/orpheus/werbung/action $ identify -verbose action_schulungsvideo_v3_print_X-3.pdf
Image: action_schulungsvideo_v3_print_X-3.pdf
Format: PDF (Portable Document Format)
Class: DirectClass
Geometry: 612x859+0+0
Resolution: 72x72
Print size: 8.5x11.9306
Units: Undefined
Type: ColorSeparation
Base type: ColorSeparation
Endianess: Undefined
Colorspace: CMYK
Depth: 16/8-bit
Channel depth:
cyan: 8-bit
magenta: 8-bit
yellow: 8-bit
black: 8-bit
Channel statistics:
Cyan:
min: 0 (0)
max: 65535 (1)
mean: 8331.78 (0.127135)
standard deviation: 14902.2 (0.227392)
kurtosis: 1.62171
skewness: 1.7799
Magenta:
min: 0 (0)
max: 62194 (0.94902)
mean: 6739.34 (0.102836)
standard deviation: 14517.5 (0.221523)
kurtosis: 2.08183
skewness: 1.93276
Yellow:
min: 0 (0)
max: 65535 (1)
mean: 13310.1 (0.203098)
standard deviation: 17022.5 (0.259746)
kurtosis: 0.991135
skewness: 1.45216
Black:
min: 0 (0)
max: 56540 (0.862745)
mean: 7117.47 (0.108606)
standard deviation: 16803.7 (0.256408)
kurtosis: 3.02752
skewness: 2.16554
Image statistics:
Overall:
min: 0 (0)
max: 65535 (1)
mean: 8874.66 (0.135419)
standard deviation: 15850.6 (0.241864)
kurtosis: 2.17614
skewness: 1.88139
Total ink density: 292%
Rendering intent: Undefined
Interlace: None
Background color: white
Border color: cmyk(223,223,223,0)
Matte color: grey74
Transparent color: black
Compose: Over
Page geometry: 612x859+0+0
Dispose: Undefined
Iterations: 0
Compression: Undefined
Orientation: Undefined
Properties:
date:create: 2011-09-14T15:39:30+02:00
date:modify: 2011-09-14T15:39:30+02:00
pdf:HiResBoundingBox: 612.28x858.9+0+0
pdf:Version: PDF-1.3
signature: 0416db7487ea147b974ece5748bc4284e82bfc3fb7cd07a4de050421ba112076
Artifacts:
verbose: true
Tainted: False
Filesize: 2.103MBB
Number pixels: 526KB
Pixels per second: 5.25708PB
User time: 0.000u
Elapsed time: 0:01.000
Version: ImageMagick 6.6.5-6 2011-04-08 Q16 http://www.imagemagick.org
This is on 64bit Gentoo with gs 9.04 Maybe that helps?
Source PDF stems from inkscape pdf export, colors were restricted to those covered in ECI ISO coated v2. I use this as a workaround for the lacking CMYK export of inkscape and the lacking prepress-ready PDF/X output...