[Gimp-user] Applying large blur only to selection

[Olivier Lecarme]

Leonard Evens <len at math.northwestern.edu> wrote:

> On Sun, 2009-05-31 at 08:39 +0200, Sven Neumann wrote:
> > Hi,
> > 
> > On Sat, 2009-05-30 at 21:24 -0500, Leonard Evens wrote:
> > > I want to blur the sky so that only pixels in the selection are used in
> > > computing the new values.  Also, I need to use a large blur radius.
> > > I've done this in the past by starting off with a small blur raidus and
> > > progressively reducing the selection, increasing the (gaussian) blur
> > > radius as I did so.  What is the simplest way to do  this?   If I just
> > > apply a gaussin blur with a large radius  to my selection is uses values
> > > outside the selection in calculationg the new values near the boundary
> > > of the selection.
> > 
> > Copy your selection, paste it to a new layer and blur that layer. Does
> > that give the desired result?
> 
> I don't believe so.   I tried it.   It still used pixels outside the
> selection in computing the new pixel values in the desired region.  In
> this case, those values were zero, so that lightened the region at the
> edges.

Did you check the "Lock alpha channel" button in the Layers dialog?

-- 


			Olivier Lecarme