El jue, 26-03-2009 a las 21:43 +0100, yahvuu escribió:
> Hi all,
> just to be shure (i'm probably just paraphrasing Andrew A. Gill's follow-up):
> I think this task can be done equally well in an RGB space, say sRGB.
> If Pantone's Bridge has sRGB approximations, it should be trivial. If not,
> you have to convert that single color from your best-guess CMYK to sRGB first.

It won't be useful if the image has to be imported in a program that
actually lets you assign CMYK values.
Following with my example, the bitmap could be imported into scribus and
put together with a logo, with the right CMYK values.
Chances are that, though quite similar, the colors won't be the same.

> Thanks to GEGL's dynamic nature, the sRGB->CMYK separation will be "live", so
> the resulting CMYK can be cross-checked immediately, like read-after-write 
> with
> good old audio tapes.

But it will still be difficult to specify a color. For instance: I need
the background of the image to be C=60%, K=100%.
I'd use that combination because I want a rich black with cold shades of
If I use RGB, the separation will include Magenta and Yellow depending
on the output profile and I wouldn't want that.

> Please do so. The general need for CMYK support beyond mere color separation
> has been put out quite clearly. Yet AFAIKS none of the examples has shown a
> requirement for doing actual image processing in CMYK space (which is
> a good thing, btw). By this i mean anything which can't be done by processing
> the "plates" as separate grayscale channels (see Øyvind Kolas's post).

It's fine to adjust the grayscale channels if we get a corrected preview
interactively. In fact, that's the way you do some adjustments in
But there are several tools (channel mixer, curves) that is useful to
have working in CMYK space.


Also, in this discussion it seems that it was never considered that you
can be working on images that somebody else sent you and you don't
control how they were created.
If somebody sent you a separated tiff of a magazine ad and you have to
do some editing on it, you'll be destroying the original separation
converting it to RGB. And that's unacceptable.

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