[XeTeX] Grey fonts with XeTeX

[Philip Taylor]

David Carlisle wrote:
> see the color package documentation
>
> \color[cmyk]{0.1,0.2,0.3,0.4} hello

Zdenek Wagner wrote:
> if you want to use the colour feature of the OpenType fonts, only RGB
> is supported. The color package allows you to use both CMYK and
> grayscale (both are allowed in the printing industry). You can, of
> course, set the colour by promitives. You have to use both k and K for
> CMYK and both g and G for grayscale (r and R are for RGB). We have a
> nice article on simple graphics in CSTUG Bulletin, but only in Czech,
> see http://bulletin.cstug.cz/doi.php/10.5300/2013-1/13
> Zdeněk Wagner
> http://ttsm.icpf.cas.cz/team/wagner.shtml
> http://icebearsoft.euweb.cz
My thanks to you both.  I am beginning to realise just how complex the world of colour is when it comes to typesetting/printing (a fact of which I have remained in blissful ignorance until now).  I am also starting to think that the pre-flight check for "List non B/W objects" in Adobe Acrobat 7.1 are not as reliable as one might hope -- the behaviour does not seem to be deterministic, nor does it appear to tally with reality :  all six pages of the PDF generated by code below are reported as "Object uses black only is not true".   But I am even more confused to discover that in XeTeX, the first four blocks all yield visibly black-on-white text, yet only two instances yields true black while two of the others yield RGB black and the fifth yields RGB white -- this must indicate that I do not understand the function of the "transparency" byte in XeTeX's font syntax.  And the sixth and final block yields RGB black despite the call to \color [cmyk] ...

\nopagenumbers

\input eplain

\beginpackages

\usepackage {color}

\endpackages

\font \thisfont = "Arial Unicode MS"

\thisfont

I appear in black-on-white and am true black (0.0)

\vfill \eject

\font \thisfont = "Arial Unicode MS:color=000000"

\thisfont

I appear in black-on-white and am RGB black (0/0/0)

\vfill \eject

\font \thisfont = "Arial Unicode MS:color=FFFFFF"

\thisfont

I appear in black-on-white and am true black (0.0)

\vfill \eject

\font \thisfont = "Arial Unicode MS:color=0000007F"

\thisfont

I appear in black-on-white and am RGB black (0/0/0)

\vfill \eject

\font \thisfont = "Arial Unicode MS:color=FFFFFF7F"

\thisfont

I appear in white-on-white and am RGB white (1/1/1)

\vfill \eject

\font \thisfont = "Arial Unicode MS:color=000000"

\thisfont \color [cmyk] {0.1, 0.2, 0.3, 0.4}

I appear in black-on-white and am RGB black (0/0/0) despite the call to \string \color \space [cmyk] ...

\vfill \eject


\end

-- 

Philip Taylor
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