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

[Robert Krawitz <rlk alum mit edu>]

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).

> 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.

> 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.

-- 
Robert Krawitz                                     <rlk alum mit edu>

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