[Qgis-developer] Open source API to convert raster to polygons?

Ricardo Scachetti Pereira ricardo at tdwg.org
Wed Jan 9 10:15:04 EST 2008

    Hi all,
    Does anyone know of any open source geoprocessing APIs that I can 
use to convert raster maps into polygons (as a shapefile or SQL for 
PostGIS)? Does QGIS do that?

    I know that GDAL (via gdal_contour utility) can turn a raster into 
lines, but that's not good enough for me. I need closed polygons that I 
later intend to import into PostGIS. Gdal_contour would give usable 
intermediate results (i.e, it produces lines that I think can be turned 
into closed polygons), if it wasn't for the open polygons that are 
created where the grid values touch NODATA values.

    I have considered using GRASS (r.poly) but I need to embed the 
geoprocessing library on an research application that I will deploy to 
Windows desktop computers. To be completely honest, I can't even 
install  GRASS on my Windows workstation, so I have no hopes of 
deploying it via a neat installer :(( . That's probably due to the lack 
of intelligence and patience, and is another story.

    Any help with this would be greatly appreciated.


Ricardo Pereira
Software Engineer and GIS Application Developer



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