I am trying to produce a CMYK PDF file to pass onto a printshop.
When I use the [cmyk] option for the xcolor package, the colours in the resulting PDF do look muted and less vibrant as is the case with the CMYK colorspace. For example,
\documentclass{minimal}
\usepackage[cmyk]{xcolor}
\begin{document}
\textcolor{blue}{\fontsize{24}{28}\selectfont A}
\end{document}
when processed by pdflatex produces a PDF file that appears onscreen like a muted, darkish CMYK colorspace document, but when I run ImageMagick's identify
command on the PDF using
identify -verbose cmyk.pdf | grep Colorspace
I get
Colorspace: RGB
Surely the PDF uses only one of CMYK or RGB for colour. How can I reliably tell which?
Also, if it is indeed an RGB PDF why does it appear so different from the version I get if the line
\usepackage[cmyk]{xcolor}
is replaced by
\usepackage[rgb]{xcolor}
Thanks in advance.
[cmyk]
causesxcolor
to automatically transfrom RGB colors to cmyk (unless it already knows the result), doesn't it? If so: the conversion RGB -> cmyk in xcolor is acceptable, but it could be better. Ah: it is mentioned in @ChristianLindig's link: "which are not very sophisticated -- compare them to the formulas in 10.3 of the PDF spec, with BG(k) and UCR(k) functions, etc"