first cs depend case: brighness,contrast

[Casper Boemann]

> Here is an advantage of YUV :)
yes, and a good example of why we need those things inside the
colorstrategy, and cannot just use KisQuantum.
Another example is CMYK: try changing brightness and you'll see that
currently it has an inverse effect. :-)

> In YUV, brightness/contrast applies to luma channel only, leaving both
> chromas unchanged.
just be aware that luma is not luminance

THIS by the way is a good time to ask: do we want say brightness filter  to
produce the exact same visual effect independent of colorspace or is
approximation good enough.

I'm not talking of letting the effects be totally wrong, but more like the
artist choosing to do it in CMYK,LAB or whatever because it produces a
slightly different effect.

Personally I think that say brighness filter should produce the exact same
visual effect in every colorspace.
doing:
RGB >> change brightness+5
should equal exactly (except for rounding errors)
RGB >> CMYK >> change brightness+5 >> RGB

If it is even possible without taking profiles into consideration is
questionable, but something to strive for I think.

best regards / venlig hilsen
Casper Boemann