Re: [Gimp-docs] Gimp-2.9.5 - Select border

[Ell <ell_se yahoo com>]

(Replying to prokoudine's mail because I don't have the original.
Please keep me CCed if you need my attention.)

On 03/17/2017 06:32 PM, Alexandre Prokoudine wrote:
> On Sat, Mar 11, 2017 at 8:37 PM, Julien Hardelin wrote:
> > Hello all,
> >
> > Please, what do you get when using select/border? I cann't see any
> > difference between the three options of "Border Style': Hard, Smooth and
> > Feather.


The main difference between "smooth" and "hard" is that "smooth" keeps
antialiasing, while "hard" doesn't.  See [1] for a comparison of the
three modes (you might need to zoom in to see the difference between
"smooth" and "hard".)  Note that "smooth" doesn't add any antialiasing
that's not already there -- if the original selection is not
antialiased, there should be no, or little, difference from "hard".

Don't know if this belongs in the docs, but on a technical level,
"hard" uses a threshold to determine the selection's outline (the same
outline shown by the marching ants), and produces a fully-selected
border around it, while "smooth" grows the original selection by half
the radius, shrinks the original selection by half the radius, and
subtracts the shrunk selection from the expanded one.

"Feathered" does the same things as "hard", but instead of the
resulting border being fully selected, it fades outwards.  The result is
pretty low-quality, though; if you need a feathered border, it's much
better to use one of the other modes, and then feather the result.  It's
there mostly for historic reasons.

All in all, "smooth" is what you generally want to use, "hard" might
be useful in some cases, and "feathered" is for when you're feeling
nostalgic (I actually think photoshop does something similar to
"feathered", or at least it used to, so you can also chalk it as a
"compatibility" feature :)

[1] 
https://bug764614.bugzilla-attachments.gnome.org/attachment.cgi?id=325383

--
Ell