[CREATE] Swatches: Proposition J

[MenTaLguY]

On Tue, 2008-06-24 at 09:37 +0200, Kai-Uwe Behrmann wrote:
> > Spot colors were actually the motivating reason for me to design the
> > format.  But having somewhat caught up with the discussion I am not as
> > satisfied with my solution as I had been.
> 
> I'd say a wide gamut reference, like CIE*Lab or CIE*XYZ, is one good 
> thing for spots. Out of my head, a name would be the other part.

The most important thing is simply the ability to say "this is a spot
color", so that an application knows to put the color on its own
separate plate with the given name.

The color specification which comes along with a spot color is actually
not that important -- it may be arbitrary and it is ignored in the final
print workflow (the print operator only looks at the name on the
separated plate).  Not all spot colors are even really colors --
consider their use in specifying varnish areas for example.

When possible and appropriate, it may also be desirable to also specify
an exact calibrated color for a spot color, to improve preview quality,
but having thought about it for a bit I think that is really an
orthogonal issue to spot colors.
 
> But it can become as well a burden to must embedd arbitrary large, 
> practical 3kB -> 3MB, ICC profiles. My go would be to have one references, 
> ideally one of the ICC deployed PCS', and one or more additional colour 
> spaces to allow for native colour descriptions without an absolute need 
> for conversions.

Using one of the standard ICC PCSs would be adequate.  The most
important thing is that, if you give someone a swatch file with
calibrated colors, you shouldn't have to do anything additional for them
to get the calibrated colors.

Using xlink:href to arbitrary ICC profiles is an extremely poor
solution; aside from the need to distribute the profiles separately, it
requires that the ICC profiles be placed in the same relative or
absolute path on the users' machine that they were on the swatch
creators'.

This is the same reason that most standards like PNG, TIFF, etc. only
support direct embedding of ICC profiles, despite the fact that profiles
can get rather large.

> So practically, making the rendering intent optional and defaulting to 
> zero, plus some warning and a small explanation why, like the above, would 
> be good to have associated to a rendering intent part in the draft.

I think that is reasonable.

> Can Cmyk channels go from 0...1 or 0...100?

The value indicating "full saturation" varies between file formats (and
sometimes even within the same one).  There is no "official" range for
CMYK or most any other color model.

-mental
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