Script (or some other means) to convert RGB to CMY

问题:

Is it possible to write a script for Adobe Illustrator or some other tool that will read the contents of a number of PDF files and convert all the RGB colours to CMYK?

If so, could somebody please point out some of the steps involved, or where to find more information on this?

回答1:

This answer is not for Illustrator, but for 'some other tool', namely Ghostscript (download gs871w32.exe or gs871w64.exe).

Ghostscript allows you to 're-distill' PDFs (without an intermediate conversion to PostScript, the dreaded 'refrying' detour). Try this command:

gswin32c.exe ^
    -o c:/path/to/output-cmyk.pdf ^
    -sDEVICE=pdfwrite ^
    -dUseCIEColor ^
    -sProcessColorModel=DeviceCMYK ^
    -sColorConversionStrategy=CMYK ^
    -sColorConversionStrategyForImages=CMYK ^
     input-rgb.pdf

And if you are able to wait for a few more weeks, Ghostscript 9.00 will be released. This new version will sport support of colormanagement (based on LCMS) with ICC profiles for the first time ever...

UPDATE: I updated above command because I missed to put in the option to also convert images.

---

Update 2

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...

1. your Ghostscript probably is a newer release from the 9.x version series, and
2. 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.

回答2:

ABCpdf will recolor to CMYK or any other color space or profile you can think of. See:

http://www.websupergoo.com/helppdf7net/source/8-abcpdf6.operations/3-recoloroperation/1-methods/recolor.htm

回答3:

I have written and tested the following script in Illustrator CC 2017:

var folder = Folder.selectDialog();
if (folder) {
    var files = folder.getFiles("*.pdf")
    for (var i = 0; i < files.length; i++) {
        app.open(files[i]);
        var doc = app.activeDocument;
        app.executeMenuCommand('doc-color-cmyk');
        doc.close(SaveOptions.SAVECHANGES);
    }
}

This script will ask for a folder, so select the folder that have your PDF file in. It will convert all PDF files in the selected folder to CMYK.

回答4:

On Linux Mint / Ubuntu, I have tried that (from this) using ICC Profiles (Ghostscript 9.18, which don't like "-dUseCIEColor"):

gs -o output.pdf -sDEVICE=pdfwrite -r2400 -dOverrideICC=true -sOutputICCProfile=/usr/share/color/icc/Fogra27L.icm -sColorConversionStrategy=CMYK -dProcessColorModel=/DeviceCMYK -dRenderIntent=3 -dDeviceGrayToK=true input.pdf

It "seems" to work (-r2400 is useful; it's for the resolution, it can be changed or removed).

Maybe adding "-sDefaultRGBProfile=/usr/share/color/icc/colord/sRGB.icc" could be better for the input... I don't know (and I don't know where). Maybe an expert could explain the best way to use.

Thanks. Regards,