I Glynn, Thanks for the reply. I was thinking (and must confess, I was wishing) that with r.mask those pixels that are outside of the mask (i.e. is NULL) can by skiped during the processing. Anyway, pretty thanks.
milton 2009/7/7 Glynn Clements <gl...@gclements.plus.com> > > Milton Cezar Ribeiro wrote: > > > Just suppose I have a very large - and irregular - region, and that > > I am running r.neighbors to compute some moving windows stats. As my > > region is irregular, many of central pixels will be NULL. If I use > > r.mask, it means that when I run r.neighbours the processing will be > > faster than when I not set r.mask (supposing that the north, south, > > west and east will be the same on both case)? > > There's no point in using r.mask to mask out pixels which are already > null. The mask simply forces specific pixels to be read as null; to > the module, such nulls are indistinguishable from nulls in the > original data. > > -- > Glynn Clements <gl...@gclements.plus.com> >
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