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

[Gez <listas ohweb com ar>]

El dom, 03-05-2015 a las 13:32 -0400, Robert Krawitz escribió:
> On Sun, 03 May 2015 02:34:26 -0300, Gez wrote:
> > 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.
>
> I agree, but draw a very different conclusion (my conclusion is in
> line with Elle's).

Then what? Every single operation and the layer stack in GIMP should
have an extra checkbox for selecting how alpha will be treated? We can
go on forever with examples like this, adding checkboxes for every
possibility. Are you saying that this is a good way to design a user
interface?
> > 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.
>
> Right.  The problem is when you're one of the people who *do* care
> about it.

I took this example because I do care about alpha channels. There are
some conventions about how to use alpha channels properly and I think
it's reasonable to expect that the program I use adheres to those
conventions.


> > And believe me, when it comes to alpha channel THERE IS right and wrong,
> > no matter what the artist says.
>
> Perhaps, but someone may have a reason to want a particular workflow,
> even if that reason is nothing more than demonstrating what's wrong
> with it.

If I have to show the nasty effects of a wrong manipulation of the alpha
channel, GIMP already gives me the tools to do that.
If I have to show the nasty effects of doing an alpha over composite in
gamma space, well, I don't have to do anything currently, but I could do
it as well with a tool that offers only linear compositing and a
gamma/curves/levels tool.

I'm just arguing against adding checkboxes arbitrarily just in case the
user wants to do anything. That's bad UI design.
I'm trying to discuss the costs and benefits of adding that complexity.
Isn't this achievable with different tools and methods? Is it needed so
frequently that is reasonable to add an extra checkbox to every single
operation?
Nobody answers that.