[cairo] Spot colors (and CMYK)

Kai-Uwe Behrmann ku.b at gmx.de
Sun Feb 14 23:41:33 PST 2010

Am 14.02.10, 23:31 -0400 schrieb cu:
> FWIF, from a user of Cairo - please for the love of all that is good -
> keep it simple.  Cairo is complicated enough as it is. As a user, I'd
> vote for keeping the crucial stuff in, the esoteric out and getting it
> done. No one product can please everyone, nor should it. As it stands,
> sRGB is exactly the right choice for most software development and it's
> important to get it right (check!) and keep it right.

sRGB in cairo is broken.

That people tend to make assumtions about their devices to be sRGB does 
not solve the problem of having different colour output on each monitor.

For instance the quartz backend makes assumtions all over the place about 
colour spaces. Interesstingly it is not sRGB but GenericRGB
(CGColorSpaceCreateDeviceRGB OS X v10.4 and later). GenericRGB is 
different from sRGB. If it would be sRGB it would diverge from Linux 
output and user will comply that to be broken. And as it looks different 
to main osX apps, say Preview or the Finder, it is broken as well.

The native osX API really shines with ease of use. One colour input 
multiple adapted outputs. That is clear design, consequent implementation 
and results in consistent appearence across devices.
As I said above, the typical unmanaged cairo output in comparision looks 
broken as sRGB in the context of the actual cairo API means all and 

Thats all no issue for a black and white word processor, as typical no one 
will simulate paper white in screen just to print black text ;-)
But for skin tones in a family photo album it is a problem: "Grand daddy 
looks on your monitor better then on mine."

To solve that brokeness, application developers need messy extra code for 
each OS they want to port to and avoid a large part of cairo APIs.
Thats in my opinion neighter easy nor the "right choice".

kind regards
Kai-Uwe Behrmann
developing for colour management 
www.behrmann.name + www.oyranos.org

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