Re: [NTG-context] Metapost and CMYK

luigi scarso wrote:

On 2/2/07, Peter Rolf wrote:

...

Hi all,

I have some questions about cmyk in combination with Metapost. Just by using

\setupcolors[state=start, cmyk=yes, mpcmyk=yes, rgb=no, ]

I get cmy(k=0) graphics, although all used colors are still defined in the rgb color space. This is really a nice feature and the automatic color conversion works relative good. Only (so far I have seen) gray tones have a noticeable tendency to brown (Acroreader 7.09). I have tested one of those gray tones by defining it as cmyk and the result looks ok.

RGB(223,223,227) CMY(0.12548, 0.12547, 0.10980) CMYK(0.01762, 0.01760, 0, 0.10980)

So is there a way to get cymk instead of cmy?

hmm, can you post an example ?

Mojca has pointed me to the definition of \convertRGBtoCMYK (colo-ini.tex) and (if I understand it right) this is only a RGB->CMY conversion. The algorithm for the missing CMY->CMYK conversion is simple (see http://www.easyrgb.com/math.php?MATH=M13#text13 ), but "exact" calculation in TeX is no fun at all (at least not for me). I have tried to implement it, but yet without success. In the worst case I have to wait for luatex, which will solve all calculation problems. So think twice, before you waste your time... ;) Maybe I should add this color conversion to the feature request list, so that it will not be forgotten? Peter

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