"Øyvind" == Øyvind Kolås <pippin@...85...> writes:
Øyvind> CIE Lab have no advantage over for instance linear light RGB using for Øyvind> instance the sRGB primaries. It actually has disadvantages as CIE Lab Øyvind> fails to be the perceptually uniform color space it aims to be, and Øyvind> hue shifts are introduced when you move colors towards the neutral Øyvind> axis in the space.
Perceptually uniform is better, yes, but I question converting to *any* RGB space when the output is to be reflective. It might be OK for flex when printing transparent/translucent labels, but for printing on opaque surfaces???
Øyvind> A linear light RGB space with well defined primaries would be Øyvind> based on reality (physics) and not an ad-hoc model trying to Øyvind> describe the subjective human experience of colors. Failing that Øyvind> CIE XYZ could be used, but that provides little meaning.
That model, empirically, works. And the point of the question was to support the needs of the prepress community.
Øyvind> No, you cannot convert from CMYK to any RGB, CIE Lab, CIE XYZ or Øyvind> similar three dimensionsal color space, and back again to CMYK Øyvind> w/o losing information contained in the original CMYK buffer.
The fact that we only have three cones implies that any colour differences found in a CMYK file can be represented in XYZ and 3D spaces derrived therefrom, even if the raw math seems to loose data.
It is always healthy to look at things from several viewpoints and to debate, but inkscape really shouldn't convert to RGB internally except when the output is to be RGB.
Personally, I've come to like LogLuv as a working space:
http://en.wikipedia.org/wiki/Logluv_TIFF http://www.anyhere.com/gward/papers/jgtpap1.pdf http://www.anyhere.com/gward/pixformat/tiffluv.html
(Given that vector art will likely only /specify/ a small number of colours--as opposed to caculate, as in gradients, filters and such-- I'd use the full 48-bit version of logLuv for calculations, colour dialogs, etc. The 32-bit or 24-bit versions are better for photos and other raster art.)
-JimC