alpha and non-alpha models

[Casper Boemann]

On Friday 18 March 2005 10:05, Boudewijn Rempt wrote:
> I've wondered about the same thing myself. There may be a problem in user
> expectations: the eraser tool has a different meaning in alpha and
> non-alpha situations.
Hadn't thought of that but it could be an option of eraser to act as if there 
is no alpha.

> And there's not really something like cmyk + alpha 
> (outside Krita :-). On the other hand, one of my perennial issues with
> applications like the Gimp and Photoshop is that I don't automatically have
> an alpha channel in imported images.
hmm,  I just played with photoshop and both rgb and cmyk have alpha natively. 
The channel is not default visible though, but if you erase with 50% opacity, 
you see the layer below shine through. In fact: if you have layers you have 
alpha. Otherwise how would you have transparent areas of layers

>
> Another issue is using the lcms transforms. There are no cmyk + a icc
> profiles, whicn means that doing a transform using lcms is kinda hard.
> That's the reason there are still two cmyk classes: one uses lcms, the
> other formulas. But cmyk is still broken, and I guess we're not going to
> get it fixed before the release.
but it should be possible right?
>
> > Alpha is heavily used in most parts of krita, so why don't we just limit
> > ourselves to RGBA, CMYKA, LABA.
> >
> > Only place where this is somewhat impossible is indexed (which we dont'
> > have yet and may never have) and even that could have a boolean alpha
>
> I don't think we need indexed color models. But I'm not sure what happens
> with other models -- like the hsv-like models or the the more complex
> things like wet & sticky -- if you must have alpha.
Well alpha is just transparency, on a per pixel scope, so ANY kind of 
colormodel should be able to support it.

The only problem is indexed, because when viewing it produces new mixes of 
colors that possible isn't in the palette. With boolean alpha it's either one 
color or the other, so no new colors are mixed.

-- 
best regards / venlig hilsen
Casper Boemann