[cairo] Spot colors (and CMYK)

Chris Murphy lists at colorremedies.com
Wed Jan 20 16:41:57 PST 2010

On Jan 20, 2010, at 7:26 PM, James Cloos wrote:

>>>>>> "Chris" == Chris Murphy <lists at colorremedies.com> writes:
> Chris> Why scRGB and not OpenEXR? Is this in the archives somewhere?
> It should be; try searching for scRGB in posts by Carl.
> The idea is that cairo already asks for doubles for colourant values,
> scRGB has the same primaries and transform as sRGB when viewed as reals,
> the doubles are allowed to have any value a double can represent, so
> therefore the two spaces are identical until conversion to integer
> values is done.
> Or at least that is what /I/ got out of the posts.

I don't know if I find this more compelling compared to RIMM/ROMM, especially in an ICC context. There have been more challenges testing perceptual sRGB to print conversions, than a compositing/intermediate space based on an output medium metric. There's a greater difference in the shape of sRGB  and output color gamuts, compared to a reference input/output medium approach, especially considering the sRGB blue primary compared to printers, and even today's LCD displays.

In any event, OpenEXR only came up once in my search and is unrelated to this discussion. And scRGB only comes up twice and neither explores alternatives. RIMM and ROMM don't come up at all. I can see why something needs to be picked as a default, but will it be possible to specify something other than scRGB?

Anyway, for encoding spot colors, I see no meaningful advantage to encoding them in scRGB, and every reason why they should be encoded as XYZ/LAB or better, spectrally.

Chris Murphy
Color Remedies (TM)
New York, NY
Co-author "Real World Color Management, 2nd Ed"

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