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

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

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
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>

***  MIT Engineers   A Proud Tradition  ***
Member of the League for Programming Freedom  --
Project lead for Gutenprint   --

"Linux doesn't dictate how I work, I dictate how Linux works."
--Eric Crampton

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