Le lundi 26 janvier 2015 15:18:43, Jukka Rahkonen a écrit :
> Spotted from gis.stackexchange:
>
> http://gis.stackexchange.com/questions/131765/ogr-dxf-closed-polyline-conve
> rsion
>
> The DXF driver documentation claims that closed polylines from DXF are
> converted into polygons but that does not seem to happen. By comparing the
> DXF snipped from stackexchange
>
> ENTITIES
> 0
> LWPOLYLINE
> 5
> 20000
> 8
> 0
> 100
> AcDbEntity
> 100
> AcDbPolyline
> 70
> 1
> 90
> 4
>
> with a DXF specification
> http://www.autodesk.com/techpubs/autocad/acad2000/dxf/lwpolyline_dxf_06.htm
> I can read that LWPOLYLINE [code 70] is defined with flag 1 [closed]. But
> could someone interpret what does it mean in GIS context? Should a closed
> CAD polyline be translated into LINEARRING or POLYGON in WKT?
Jukka,
It seems the documentation matches the initial implementation but has been
outdated by later changes. Indeed, ogr/ogrsf_frmts/dxf/ogrdxflayer.cpp contains
the following (disabled) code :
/* -------------------------------------------------------------------- */
/* If polyline is closed, convert linestring to a linear ring */
/* */
/* Actually, on review I'm not convinced this is a good idea. */
/* Note that most (all) "filled polygons" are expressed with */
/* hatches which are now handled fairly well and they tend to */
/* echo linear polylines. */
/* -------------------------------------------------------------------- */
#ifdef notdef
if(m_bClosed)
{
OGRLinearRing *poLR = new OGRLinearRing();
poLR->addSubLineString( poLS, 0 );
delete poLS;
// Wrap as polygon.
OGRPolygon *poPoly = new OGRPolygon();
poPoly->addRingDirectly( poLR );
return poPoly;
}
#endif
Only HATCH (as well as 3DFACE and SOLID) objects are converted as Polygon.
Even
>
> -Jukka Rahkonen-
>
>
>
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