Re: [Gimp-developer] GIMP useability - choosing linear vs perceptually uniform RGB

[Gez <listas ohweb com ar>]

El sáb, 02-05-2015 a las 12:40 -0400, Elle Stone escribió:

> Well, you might be able to answer that question. I'm not qualified.
> Personally I don't use alpha channels except in the extremely rare 
> instance when I'm exporting a png with a transparent background for use 
> on a website.

See, this is exactly what I intended to discuss.
You know a lot about linear and perceptual gamma, so in your opinion
everything has to be tailored to allow you to play as you wish with
gamma. For you it is essential.
Now, you think you don't use alpha channels, so you don't care much
about the options provided. But you actually use alpha channels a lot:
every time you create a layer mask you're creating an alpha channel for
that layer, and if that alpha is associated or unassociated makes a big
difference.
AFAIK, most of the time alpha channel is unassociated in GIMP, but when
you have to apply any convolution you have to "pre-multiply" it.
And what about alpha channels being linear or perceptual? Why don't you
care?
In that case, developers chose for you, and you don't seem to feel too
bad about it.
And believe me, when it comes to alpha channel THERE IS right and wrong,
no matter what the artist says.
Blending modes and other operations have been designed to work in
certain way. They have an intended result.
Unfortunately limitations in the available technology in the past forced
programs to do things as alpha compositing in 8 bit gamma.
It looks like shit but users got used to that appearance. That doesn't
mean that alpha compositing in gamma space is ok and it is a valid
option so programs SHOULD allow it.
It's an infortunate legacy that could be corrected by making the tool
work as it should work, as it is intended to work.
Some people may want having the uglyness back, so a special (optional)
tool to override the proper behavior with that crap could be used.

Personally, I'd love to see all the operations work on linear data only.
If a mechanism for overrides is in place, getting legacy support would
be probably just matter of setting a global override making everything
work in gamma.
In both cases an extra tool could allow flipping stuff to the other
"mode" temporarily. In the case of gamma we've been discussing it is
something that seems to be just one "gamma node" away.
Actually, you don't even need that. with enough bit depth the levels
tool alone is good for making gamma stuff more or less linear and linear
more or less perceptually uniform, for artistic purposes. And since you
don't seem to worry about "right" or "wrong" results, that should
suffice.

Gez.