[GRASS-user] Fwd: How to obtain selected adjacent pixel values?

[Nikos Alexandris]

[..]

Nikos A:
> >> Please check the manual of r.mapcalc.  There is  "THE NEIGHBORHOOD 
> >> MODIFIER"  which I think can be used to obtain what is asked.
> >> So, for each of the off-current pixel, the modifiers would be like
> >> RASTER_IN_PUSHED_ONE_ROW_UP:  map[-1,0]
> >> RASTER_IN_PUSHED_ONE_ROW_DOWN:  map[1,0]
> >> RASTER_IN_PUSHED_ONE_COLUMN_LEFT:  map[0,-1]
> >> RASTER_IN_PUSHED_ONE_COLUMN_RIGHT:  map[0,1]

Markus Metz wrote: 
> r.mapcalc \
> "RASTER_OUT=round(abs((RASTER_IN - RASTER_IN[0,-1]) + \
> (RASTER_IN - RASTER_IN[0,1]) + \
> (RASTER_IN - RASTER_IN[-1,0]) + \
> (RASTER_IN - RASTER_IN[1,0])))"

> Note that this is the same like
> round(abs(4 * RASTER_IN - \
> (RASTER_IN[0,-1] + \
> RASTER_IN[0,1] + \
> RASTER_IN[-1,0] + \
> RASTER_IN[1,0])))

[..]

Maybe we can add this example in the manual?

Nikos