alpha and non-alpha models

[Boudewijn Rempt]

On Friday 18 March 2005 00:01, Casper Boemann wrote:
> Hi
>
> I was just wondering.
>
> do we even want both alpha and non-alpha versions of colormodels.

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. 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.

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.

> 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.

> when loading a non-alpha image it would be as simple as adding alpha
> values, and storing, even now involves flattening the image so most alpha
> is lost.

That's going to change soon, though: I'm going to Brussels tonight so I've got 
a nice, long train journey in a train with electrical outlets and a night in 
a boring hotel to hack in.

> So out with RGB - we have RGBA
> CMYK should be CMYKA and so on

Actually... That's already true for rgb and gray.

> for UI porposes we should not mention A

It might be necessary to explain this design decision in the manual because 
people accustomed to the Gimp or Photoshop will miss the option.

-- 
Boudewijn Rempt 
http://www.valdyas.org/fading/index.cgi
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