> I think CMYK support in tools used early in the publishing chain
> is somewhat overrated.

Right, but FOP _MUST_ not be early in the publishing chain! It could
in fact be the only and therefore even the last step in a publishing
chain...


> I can only think of the following use cases for XSLFO:
> - Avoid round-off errors and other numerical problems in the
>   conversion CMYK->sRGB->CMYK, perhaps in order to match exactly
>   colors of embedded CMYK bitmap images in text, borders and
>   background.

Conversion CMYK -> RGB is nearly always lossy. And for print sRGB 
is also not that perfect (because of it's small gammut (nearly the 
smalest gammut of all RGB colorspaces)).


> - Get color values into the document which can't be expressed
>   as RGB. I don't know whether this can even happen.

If you create PDFs for print, you nearly always want CMYK! Okay, 
RGB and colorspace would be great but nowaday not all print-
companys now how to handle colorspaces (for example PDF/X-3).


>
> As far as round-off goes, AFAIK the transformation from CMYK to
> RGB and vice versa is linear and numerically well behaved with
> the exception of some extreme saturated colors, in particular
> very dark colors. I've never heard of anyone noticing these
> kind of problem without deliberately using a somewhat braindamaged
> tool for colorspace conversion which rounded all values to two
> significant digits *and* both a quite expensive printing kit and
> a well trained eye.

100% c                                  83% c
  0% m                                   5% m
  0% y  -->     sRGB            -->      2% y
  0% k                                   0% k

So in fact, CMYK -> sRGB -> CMYK is not linear. If you convert the 
result to sRGB and again back the values will even be more bad.

> 
> J.Pietschmann
> 
> 

Christian Beer


> 

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