[GRASS-dev] Re: [GRASS-user] circle surrounding neighbors

[Martin Wegmann]

On Tuesday 31 July 2007 10:54:19 Glynn Clements wrote:
> Glynn Clements wrote:
> > > Sorry, I am a beginner... what shall I do with this gather-circle.c?
> >
> > Replace raster/r.neighbors/gather.c with the new file, re-compile,
> > install the modified r.neighbors as e.g. r.neighbors.circle.
> >
> > If you don't have the source code or can't figure out how to make the
> > necessary changes, you'll need to wait until someone integrates it
> > into GRASS.
>
> FWIW, I've added a -c flag to r.neighbors to use a circular
> neighborhood rather than a square.

great!

> I'm unsure as to whether the test should be < or <=. It's currently
> <=, but that gives "spikes" (single cells) at the four edges. Using <
> would give "flats", and would always omit the outermost row/column of
> pixels. Maybe there should be a +0.5 in the distance calculation?

then the command works like

r.neighbors -c input=name output=name method=average size=5 
and the output would be the average of values in a ring of 5x5 around the 
center pixel, wouldn't it? 

then I can drop my r.mapcalc script and close one old wish report related to 
r.le but solved via r.neighbors 
(http://www.intevation.de/rt/webrt?serial_num=2104&display=History) - thanks 
a lot!

Martin