[postgis-users] How to get the centroid of an bounding box using st_extent

[Paul Ramsey]

In particular, these ones are used by the casts.


-- Availability: 1.2.2
CREATEFUNCTION ST_geometry(box2d)
         RETURNS geometry
         AS '@MODULE_FILENAME@','BOX2DFLOAT4_to_LWGEOM'
         LANGUAGE 'C' _IMMUTABLE_STRICT; -- WITH (isstrict,iscachable);

-- Availability: 1.2.2
CREATEFUNCTION ST_geometry(box3d)
         RETURNS geometry
         AS '@MODULE_FILENAME@','BOX3D_to_LWGEOM'
         LANGUAGE 'C' _IMMUTABLE_STRICT; -- WITH (isstrict,iscachable);

Paul Ramsey wrote:
> Charlie Savage wrote:
> 
>> As an aside, its not obvious to me how to actually fix this bug. 
>> Somehow the conversion from Box2D/Box3D to geometry needs to figure 
>> out if the bbox has 0 width and/or 0 height and if so create a Point 
>> instead of a Polygon.  
> 
> The problem will live in the function that casts from Box* to GEOMETRY. 
>  PostgreSQL does automatic casting, so
> 
> Extent(GEOMETRY) return BOX*
> Centroid(GEOMETRY) returns GEOMETRY
> 
> PostgreSQL will rewrite Centroid(Extent()) to Centroid(Box2Geom(Extent())
> 
> P.
> 
> 


-- 

   Paul Ramsey
   Refractions Research
   http://www.refractions.net
   pramsey at refractions.net
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   Cell: 250-885-0632