[XeTeX] CMYK to RGB conversion in xetex.def

[Bruno Voisin]

Did anybody check the correctness of the CMYK to RGB color conversion  
code in XeTeX's definition file for the graphics package, namely 
( xetex.def?

With the hyperref package, used with the colorlinks=true option, the  
default color (linkcolor) for internal links is red, while the  
default color (urlcolor) for external links is magenta.

Now, if you compare the documentation files /usr/local/teTeX/share/ 
texmf.tetex/doc/latex/hyperref/manual.pdf for hyperref and XeTeX- 
notes.pdf for XeTeX, you'll notice the colors for internal links, for  
example in the table of contents, are the same, while the colors for  
external links are different.

Given that xetex.def works internally with RGB colors, and includes  
code for CMYK to RGB conversion, I'm wondering whether this code  
could contain an error, with the result that magenta in XeTeX isn't  
quite the same as magenta in pdfTeX.

I noticed that by trying to create, in a XeTeX document I'm writing,  
text matching exactly some colors from my lab's logo, for which I  
know exactly the Pantone and CMYK specifications (provided by the  
graphic designer who did the logo). Using CMYK colors directly, as in

     \definecolor{legidarkblue} {cmyk}{1.00,0.45,0.00,0.18}
     \definecolor{legilightblue}{cmyk}{0.90,0.10,0.00,0.00}

I wasn't getting the correct colors. But if I use first the Mac OS  
color palette (for example in TextEdit) to convert these CMYK colors  
to RGB, and use these with XeTeX, as in

     \definecolor{legidarkblue} {rgb}{0.00,0.27,0.49}
     \definecolor{legilightblue}{rgb}{0.00,0.54,0.78}

then I'm getting the correct output.

Ross, if you're listening, what d'you think?

Bruno Voisin