David Necas (Yeti) wrote:
I want a yellow opaque circle, with edges blurred to
transparent and some fine yellow pixelish haze around.
The transition I also don't like continuous, but spotty with
varying opacity, so one can see the background better or
worse through individual pixels.

Layer mask! But thanks for bringing it to our attention that Noisify is one of the broken plugins in this respect.

This isn't a new breed of brokenness that popped up when
tile-row-hints went in.  It's a fundamental problem with
how some plugins handle alpha data and it's been evident
for as long as GIMP has had alpha support.

Create a new transparent image, draw a yellow blob in the
middle, then blur the image by 10px.  I really hope
you'd expect to see a blurry yellow blob rather than
blurry blob that's yellow in the middle and black (or
worse) towards the edges... but the latter is what you
used to get until someone (Raphael?) went around finding
and fixing the various places that assumed that RGB and
alpha are logically decoupled.  They're not.  You can't
operate on them orthogonally, 'A' is not just another
dimension in 'RGBA space' -- it's simply not, but when
a tool/plugin makes this mistake it's just asking to
fall into the singularity.

In someone's mental model color values are inherently
premultiplied, and alpha == 0 means R, G, B == 0.  In
someone's alpha channels is a fourth independent value we
attached to each pixel and it doesn't directly interact with
R, G, B.  This schizm can't be solved because both model are
"correct" in some sense and in some situations.  However,
Gimp uses separate alpha channel internally thus I see as
illogical to force the other mental model.

If you wish to have an alpha-adjusting playing-field then a layer masks is conceptually an operation that gets applied to RGBA pixel data as part of the compositing step, and that's super.

Adam D. Moss   . ,,^^   [EMAIL PROTECTED]   http://www.foxbox.org/   co:3
busting makes me feel good
kthx bye

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