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How can I convert a color name (such as used with the xcolor package) to a pdfliteral code, like q 1 0 0 rg (for red)?

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What is the context here? The drivers for the color package normally deal with this for LaTeX users, as this keeps code driver-independent. Also, with a sufficiently up-to-date pdfTeX or LuaTeX, why use \pdfliteral rather than \pdfcolorstack? – Joseph Wright♦ Sep 19 '11 at 9:28
@JosephWright The context is in Lua code, and I can't use \color there because I'm inserting PDF annotations from the Lua code. – ℝaphink Sep 19 '11 at 9:30
The way that named colours are done is by defining what they convert to: a colour model and then some values. I'd imagine a Lua solution would be done the same way. Can't you just access the appropriate macro definitions from the Lua end? – Joseph Wright♦ Sep 19 '11 at 9:36
@JosephWright Sure, then I guess my question would be if there is such a macro which converts a color name into a space separated triplet of RGB components? – ℝaphink Sep 19 '11 at 9:38

1 Answer

up vote 13 down vote accepted 
\pdfcompresslevel=0 % to make everything visible in the pdf 
\documentclass{article}
\usepackage{xcolor}
\def\usecolor#1{\csname\string\color@#1\endcsname\space}

\begin{document}
foo
\pdfliteral{\usecolor{red}}
bar
\end{document}

in pdf it is: 1 0 0 rg 1 0 0 RG

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So \usecolor{red} outputs 1 0 0 rg 1 0 0 RG? – ℝaphink Sep 19 '11 at 9:48
yes, can already been seen in the pdf – Herbert Sep 19 '11 at 9:52
Yes, that works great! Thank you! – ℝaphink Sep 19 '11 at 9:54

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