I am having much trouble to get ImageMagick's <code>identify</code> to, well, identify a PDF as CMYK. Essentially, let's say I'm building this file, <code>test.tex</code>, with <code>pdflatex</code>: <pre class="prettyprint"><code>\documentclass[a4paper,12pt]{article} %% https://tex.stackexchange.com/questions/13071 \pdfcompresslevel=0 %% http://compgroups.net/comp.text.tex/Making-a-cmyk-PDF %% ln -s /usr/share/color/icc/sRGB.icm . % \immediate\pdfobj stream attr{/N 4} file{sRGB.icm} % \pdfcatalog{% % /OutputIntents [ << % /Type /OutputIntent % /S/GTS_PDFA1 % /DestOutputProfile \the\pdflastobj\space 0 R % /OutputConditionIdentifier (sRGB IEC61966-2.1) % /Info(sRGB IEC61966-2.1) % >> ] % } %% http://latex-my.blogspot.com/2010/02/cmyk-output-for-commercial-printing.html %% https://tex.stackexchange.com/questions/9961 \usepackage[cmyk]{xcolor} \begin{document} Some text here... \end{document} </code></pre> If I then try to identify the resulting <code>test.pdf</code> file, I get it as RGB, no matter what options I've tried (at least according to the links in the source) - and yet, the colors in it would be saved as CMYK; for the source above: <pre class="prettyprint"><code>$ grep -ia 'cmyk\|rgb\| k' test.pdf 0 0 0 1 k 0 0 0 1 K 0 0 0 1 k 0 0 0 1 K 0 0 0 1 k 0 0 0 1 K 0 0 0 1 k 0 0 0 1 K FontDirectory/CMR12 known{/CMR12 findfont dup/UniqueID known{dup /PTEX.Fullbanner (This is pdfTeX, Version 3.1415926-1.40.11-2.2 (TeX Live 2010) kpathsea version 6.0.0) $ identify -verbose 'test.pdf[0]' ... Type: Palette Endianess: Undefined Colorspace: RGB Depth: 16/8-bit Channel depth: red: 8-bit green: 8-bit blue: 8-bit Channel statistics: Red: ... Green: ... Blue: ... Histogram: 5: (12593,11565,11822) #31312D2D2E2E rgb(49,45,46) 4: (16448,15420,15677) #40403C3C3D3D rgb(64,60,61) 9: (20303,19275,19532) #4F4F4B4B4C4C rgb(79,75,76) 25: (23901,23130,23387) #5D5D5A5A5B5B rgb(93,90,91) ... </code></pre> The same pretty much happens if I also uncomment that <code>\immediate\pdfobj stream ...</code> part; and yet, if there is only one color (black) in the document, I don't see where does <code>identify</code> come up with a histogram of RGB values (although, arguably, all of them close to gray) ?! So nevermind this, then I though I'd better try to use <code>ghostscript</code> to convert the <code>test.pdf</code> into a new pdf, which would be recognized as CMYK by <code>identify</code> - but no luck even there: <pre class="prettyprint"><code>$ gs -dNOPAUSE -dBATCH -dSAFER -sDEVICE=pdfwrite -sOutputFile=test-gs.pdf -dUseCIEColor -sProcessColorModel=DeviceRGB -dProcessColorModel=/DeviceCMYK -sColorConversionStrategy=/CMYK test.pdf GPL Ghostscript 9.01 (2011-02-07) Copyright (C) 2010 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 $ identify -verbose 'test-gs.pdf[0]' ... Type: Grayscale Base type: Grayscale Endianess: Undefined Colorspace: RGB Depth: 16/8-bit ... </code></pre> So the only thing that <code>identify</code> perceived as a change, is <code>Type: Grayscale</code> (from previous <code>Type: Palette</code>); but otherwise it still sees an RGB colorspace! Along with this, note that <code>identify</code> is capable of correctly reporting a CMYK pdf - see CMYK poster example: fitting pdf page size to (bitmap) image size? #17843 - TeX - LaTeX - Stack Exchange for a command line example of generating such a PDF file using <code>convert</code> and <code>gs</code>. In fact, we can execute: <pre class="prettyprint"><code>convert test.pdf -depth 8 -colorspace cmyk -alpha Off test-c.pdf </code></pre> ... and this will result with a PDF that will be <code>identify</code>ed as CMYK - however, the PDF will also be rasterized (default at 72 dpi). EDIT: I have just discovered, that if I create an .odp presentation in OpenOffice, and export it to PDF; that PDF will by default be RGB, however, the following command (from ghostscript Examples | Production Monkeys): <pre class="prettyprint"><code># Color PDF to CMYK: gs -dSAFER -dBATCH -dNOPAUSE -dNOCACHE -sDEVICE=pdfwrite \ -sColorConversionStrategy=CMYK -dProcessColorModel=/DeviceCMYK \ -sOutputFile=output.pdf input.pdf </code></pre> ... actually will produce a CMYK pdf, reported as such by <code>identify</code> (although, the black will be rich, not plain - on all four channels); however, this command will work only when the slide has an added image (apparently, it is the one triggering the color conversion?!)! Funnily, I cannot get the same effect from a <code>pdflatex</code> PDF. So I guess my question can be asked two ways: <ul> <li>Are there any command-line conversion methods in Linux, that will convert an RGB pdf into a CMYK pdf while preserving vectors, which is recognized as such in <code>identify</code> (and will consequently build a correct histogram of CMYK colors)</li> <li>Are there any other command-line Linux tools similar to <code>identify</code>, which would recognize use of CMYK colors correctly even in the original <code>test.pdf</code> from <code>pdflatex</code> (and possibly build a color histogram, based on an arbitrarily chosen PDF page, like <code>identify</code> is supposed to)?</li> </ul> Thanks in advance for any answers, Cheers! Some references: <ul> <li>adobe - Script (or some other means) to convert RGB to CMYK in PDF? - Stack Overflow</li> <li>color - PDF colour model and LaTeX - TeX - LaTeX - Stack Exchange</li> <li>color - Option cmyk for xcolor package does not produce a CMYK PDF - TeX - LaTeX - Stack Exchange</li> <li>Making a cmyk PDF - comp.text.tex | Computer Group</li> <li> colormanagement with ghostscript ? - Rhinocerus: <blockquote> Is it for instance specified as "0 0 0 1 setcmykcolor"? Or possibly rather as "0 0 0 setrgbcolor"? In the latter case you would end up with a rich black for text, if DeviceRGB is remapped to a CIE-based color space in order to get RGB images color managed. </blockquote> </li> </ul>

sdaau, the command you used for trying to convert your PDF to CMYK was not correct. Try this one instead: <pre class="prettyprint"><code> gs \ -o test-cmyk.pdf \ -sDEVICE=pdfwrite \ -sProcessColorModel=DeviceCMYK \ -sColorConversionStrategy=CMYK \ -sColorConversionStrategyForImages=CMYK \ test.pdf </code></pre> <hr> <h3>Update</h3> 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... <ol> <li>your Ghostscript probably is a newer release from the 9.x version series, and</li> <li>your source PDF likely uses an embedded ICC color profile </li> </ol> In this case add <code>-dOverrideICC</code> to the command line and see if it changes the result as desired. <hr> <h3>Update 2</h3> To avoid JPEG artifacts appearing in the images (where there were none before), add: <pre class="prettyprint"><code>-dEncodeColorImages=false </code></pre> 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 <code>pdftk</code> does {<code>pdftk</code> 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...)

Converting PDF to CMYK (with identify recognizing CMYK)

Tags:

linux

pdf

imagemagick

ghostscript

cmyk

I am having much trouble to get ImageMagick's identify to, well, identify a PDF as CMYK.

Essentially, let's say I'm building this file, test.tex, with pdflatex:

\documentclass[a4paper,12pt]{article}  %% https://tex.stackexchange.com/questions/13071 \pdfcompresslevel=0  %% http://compgroups.net/comp.text.tex/Making-a-cmyk-PDF %% ln -s /usr/share/color/icc/sRGB.icm . % \immediate\pdfobj stream attr{/N 4} file{sRGB.icm} % \pdfcatalog{% % /OutputIntents [ << % /Type /OutputIntent % /S/GTS_PDFA1 % /DestOutputProfile \the\pdflastobj\space 0 R % /OutputConditionIdentifier (sRGB IEC61966-2.1) % /Info(sRGB IEC61966-2.1) % >> ] % }  %% http://latex-my.blogspot.com/2010/02/cmyk-output-for-commercial-printing.html %% https://tex.stackexchange.com/questions/9961 \usepackage[cmyk]{xcolor}  \begin{document} Some text here... \end{document}

If I then try to identify the resulting test.pdf file, I get it as RGB, no matter what options I've tried (at least according to the links in the source) - and yet, the colors in it would be saved as CMYK; for the source above:

$ grep -ia 'cmyk\|rgb\| k' test.pdf  0 0 0 1 k 0 0 0 1 K 0 0 0 1 k 0 0 0 1 K 0 0 0 1 k 0 0 0 1 K 0 0 0 1 k 0 0 0 1 K FontDirectory/CMR12 known{/CMR12 findfont dup/UniqueID known{dup /PTEX.Fullbanner (This is pdfTeX, Version 3.1415926-1.40.11-2.2 (TeX Live 2010) kpathsea version 6.0.0)  $ identify -verbose 'test.pdf[0]' ...   Type: Palette   Endianess: Undefined   Colorspace: RGB   Depth: 16/8-bit   Channel depth:     red: 8-bit     green: 8-bit     blue: 8-bit   Channel statistics:     Red: ...     Green: ...     Blue: ...   Histogram:          5: (12593,11565,11822) #31312D2D2E2E rgb(49,45,46)          4: (16448,15420,15677) #40403C3C3D3D rgb(64,60,61)          9: (20303,19275,19532) #4F4F4B4B4C4C rgb(79,75,76)         25: (23901,23130,23387) #5D5D5A5A5B5B rgb(93,90,91) ...

The same pretty much happens if I also uncomment that \immediate\pdfobj stream ... part; and yet, if there is only one color (black) in the document, I don't see where does identify come up with a histogram of RGB values (although, arguably, all of them close to gray) ?!

So nevermind this, then I though I'd better try to use ghostscript to convert the test.pdf into a new pdf, which would be recognized as CMYK by identify - but no luck even there:

$ gs -dNOPAUSE -dBATCH -dSAFER -sDEVICE=pdfwrite  -sOutputFile=test-gs.pdf -dUseCIEColor -sProcessColorModel=DeviceRGB -dProcessColorModel=/DeviceCMYK -sColorConversionStrategy=/CMYK test.pdf   GPL Ghostscript 9.01 (2011-02-07) Copyright (C) 2010 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   $ identify -verbose 'test-gs.pdf[0]' ...   Type: Grayscale   Base type: Grayscale   Endianess: Undefined   Colorspace: RGB   Depth: 16/8-bit ...

So the only thing that identify perceived as a change, is Type: Grayscale (from previous Type: Palette); but otherwise it still sees an RGB colorspace!

Along with this, note that identify is capable of correctly reporting a CMYK pdf - see CMYK poster example: fitting pdf page size to (bitmap) image size? #17843 - TeX - LaTeX - Stack Exchange for a command line example of generating such a PDF file using convert and gs. In fact, we can execute:

convert test.pdf -depth 8 -colorspace cmyk -alpha Off test-c.pdf

... and this will result with a PDF that will be identifyed as CMYK - however, the PDF will also be rasterized (default at 72 dpi).

EDIT: I have just discovered, that if I create an .odp presentation in OpenOffice, and export it to PDF; that PDF will by default be RGB, however, the following command (from ghostscript Examples | Production Monkeys):

# Color PDF to CMYK: gs -dSAFER -dBATCH -dNOPAUSE -dNOCACHE -sDEVICE=pdfwrite \ -sColorConversionStrategy=CMYK -dProcessColorModel=/DeviceCMYK \ -sOutputFile=output.pdf input.pdf

... actually will produce a CMYK pdf, reported as such by identify (although, the black will be rich, not plain - on all four channels); however, this command will work only when the slide has an added image (apparently, it is the one triggering the color conversion?!)! Funnily, I cannot get the same effect from a pdflatex PDF.

So I guess my question can be asked two ways:

Are there any command-line conversion methods in Linux, that will convert an RGB pdf into a CMYK pdf while preserving vectors, which is recognized as such in identify (and will consequently build a correct histogram of CMYK colors)
Are there any other command-line Linux tools similar to identify, which would recognize use of CMYK colors correctly even in the original test.pdf from pdflatex (and possibly build a color histogram, based on an arbitrarily chosen PDF page, like identify is supposed to)?

Thanks in advance for any answers,
Cheers!

Some references:

adobe - Script (or some other means) to convert RGB to CMYK in PDF? - Stack Overflow
color - PDF colour model and LaTeX - TeX - LaTeX - Stack Exchange
color - Option cmyk for xcolor package does not produce a CMYK PDF - TeX - LaTeX - Stack Exchange
Making a cmyk PDF - comp.text.tex | Computer Group
colormanagement with ghostscript ? - Rhinocerus:

Is it for instance specified as "0 0 0 1 setcmykcolor"? Or possibly rather as "0 0 0 setrgbcolor"? In the latter case you would end up with a rich black for text, if DeviceRGB is remapped to a CIE-based color space in order to get RGB images color managed.

375

asked Jun 05 '11 06:06

sdaau

2 Answers

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...)

176

answered Sep 23 '22 04:09

Kurt Pfeifle

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...