[R] RGB -> CYMK, with consistent colors

[Derek Jones]

All,

I used the very useful colorspace package for the plots in my book
(pdf available here): http://knosof.co.uk/ESEUR/

The color makes the plots look great, on screen.
To get lots printed, the printer requires converting the images to use cmyk
(a common requirement for larger  printers, I'm told).  See page 11 here:
https://www.ingramspark.com/hubfs/downloads/file-creation-guide.pdf

No problem, the script below uses ghostscript to achieve this:

gs -o ESEUR-cmyk.pdf \
     -sDEVICE=pdfwrite \
     -sProcessColorModel=DeviceCMYK \
     -sColorConversionStrategy=CMYK \
     -sColorConversionStrategyForImages=CMYK \
      ESEUR.pdf

the problem is that the converted colors don't look nearly as
good.  For instance the cyan now looks blue, and prints as pure blue.

I can regenerate the images, and explicitly specify cmyk.  But using:

pdf.options(colormodel="cymk")

does not change anything.  The colors look remarkably similar to
those produced via the ghostview route.

I have been looking at color profiles and trying to find a
way of modifying an ICC profile (yes, it looks difficult).

Does anybody have any ideas for producing cmyk images that have
the same (or close enough) look as the RGB?