I am looking for an "open source" C/C++/C# Library able to convert raster to vector data (Polygonize). I know gdal_polygonize.py is doing the job, but I can't use Python. Portrace is an other option, but first it is a tool (and not a Library) and second it is not focussed on GeoData.
gdal_polygonize.py is based on the gdal_polygonize() function which doesn't require Python. So if you look at a library this would be my first choice.
Otherwise there are raster to vector writers in OTB library (but no app, as far as I know)