[Gdal-dev] ogr / geos scripting question

[Ari Jolma]

Brian Hamlin kirjoitti:
> actually, the convexHull can be a linestring in a special case, but is 
> more likely
> type 3, Polygon..  (I printed the WKT form..)
>
> I now see that you can getNumPoints(), and getPoint( index ) in C++ 
> from a LineString
> but, Polygon does not have this?

http://map.hut.fi/doc/Geo-GDAL/html/annotated.html or if that does not 
give good enough answer then I surf to 
http://www.gdal.org/ogr/annotated.html

Polygon is functionally a collection, the outer ring is the first 
geometry in it and the rest, if there are such, are inner rings (holes), 
to loop through a collection use:

if ($geom->GetGeometryCount) {
    for (0..$geom->GetGeometryCount-1) {
   }
}

To look at the vertices use (only if GeometryCount is zero):

for my $i (0..$geom->GetPointCount-1) {
        my $x = $geom->GetX($i);
        my $y = $geom->GetY($i);
        my $z = $geom->GetZ($i);
}

Ari

>
> thanks for your patience, starting out is the hardest
> best regards
>   -Brian
>


-- 
Prof. Ari Jolma
Geoinformaatio- ja paikannustekniikka / Geoinformation and positioning
Teknillinen Korkeakoulu / Helsinki University of Technology
tel: +358 9 451 3886 address: POBox 1200, 02015 TKK, Finland
Email: ari.jolma at tkk.fi URL: http://www.tkk.fi/~jolma