[GRASS-dev] [GRASS GIS] #2368: Python version of r.grow does not support shrinking

[GRASS GIS]

#2368: Python version of r.grow does not support shrinking
----------------------------------------------------------------+-----------
 Reporter:  wenzeslaus                                          |       Owner:  grass-dev@…              
     Type:  enhancement                                         |      Status:  new                      
 Priority:  minor                                               |   Milestone:  7.1.0                    
Component:  Raster                                              |     Version:  svn-trunk                
 Keywords:  r.grow, r.grow.distance, r.buffer, r.buffer.lowmem  |    Platform:  Unspecified              
      Cpu:  Unspecified                                         |  
----------------------------------------------------------------+-----------

Comment(by mmetz):

 Replying to [comment:3 glynn]:
 > Replying to [comment:2 wenzeslaus]:
 >
 > > > > I'm not sure if negative distances can be added to
 `r.grow.distance`.
 >
 > Having thought about this some more ...
 >
 > In the case where you're interested in the distance= map (rather than
 the value= map), distance inside is just as meaningful as distance
 outside.
 >
 > An r.shrink.distance module would be structurally similar (i.e. a near
 clone), so it makes sense to try to keep them in the same module.
 >
 > The easiest change would be to have an "invert" flag which caused the
 distance= map to contain the distance from the nearest null cell
 (currently, it's the distance from the nearest non-null cell, so the non-
 null cells themselves have a distance of 0).

 Attached is a minimally invasive patch to add a new flag to
 r.grow.distance, calculating the distance to the nearest null cell.

-- 
Ticket URL: <http://trac.osgeo.org/grass/ticket/2368#comment:6>
GRASS GIS <http://grass.osgeo.org>