Jeff, I believe this is exposed in ogr2ogr using the -simplify argument:
-simplify tolerance: (starting with GDAL 1.9.0) distance tolerance for simplification. Note: the algorithm used preserves topology per feature, in particular for polygon geometries, but not for a whole layer. Best regards, Frank On Tue, Feb 19, 2013 at 12:12 PM, Jeff Lacoste <jefflacosteg...@gmail.com> wrote: > Yes visually attractive or smooth polygons is the goal. Thanks again Frank. > > Doing a web search about simplification algorithm i found one named > 'Ramer-Douglas–Peucker' > (http://en.wikipedia.org/wiki/Ramer-Douglas-Peucker_algorithm). > It appears that 'Geos'' library implement this algorithm. Is this algorithm > exposed through OGR ? > > Could this algorithm help smoothing a polygon without necessary make the new > nodes too far from the original one ? Or may be there > are other *more* recommended algorithms ? > > If any one could suggest a simplification algorithm or had some experience > with smoothing polygons, I appreciate their input. > > Thanks > > Jeff > > > > > On Tue, Feb 19, 2013 at 2:42 PM, Frank Warmerdam <warmer...@pobox.com> > wrote: >> >> On Tue, Feb 19, 2013 at 11:28 AM, Jeff Lacoste >> <jefflacosteg...@gmail.com> wrote: >> > Hi Frank, >> > >> > Thanks for your quick response. Following the edges of the pixels seems >> > a >> > perfect solution for non continuous grid (ex. land use, etc.) as >> > the boundary between the class is important to keep when constructing >> > the >> > polygon. However for continuous grid (.ex elevations), the boundaries >> > are >> > a bit not clear and not clear cut. When following the pixels edges, the >> > created polygons appear to have the stairs effect and are less visually >> > attractive. >> > >> > I thought of a smoothing the polygons to not have *rough* edges using >> > the >> > current gdal_polygonize by trying to not follow the pixels edges and use >> > instead of the >> > pixel centers. Basically do something similar to what contour generator >> > does >> > by treating the raster values as continuous. >> >> Jeff, >> >> Ah, I see, you are looking for visually attractive polygons from >> continuous fields. >> >> I have wondered if it would be reasonable to produce a version of the >> contour generator that actually produces polygon regions. If we had >> that then applying appropriate simplification to the resulting very >> detailed edges should give something attractive and with reasonable >> information density. An appropriate simplification algorithm might do >> this in a reasonable way for the existing polygonize output but I >> don't know enough about the simplification algorithms to suggest one. >> >> I don't think aiming for pixel centers in gdal_polygonize would really >> solve the problem. >> >> Best regards, >> -- >> >> ---------------------------------------+-------------------------------------- >> I set the clouds in motion - turn up | Frank Warmerdam, >> warmer...@pobox.com >> light and sound - activate the windows | http://pobox.com/~warmerdam >> and watch the world go round - Rush | Geospatial Software Developer > > -- ---------------------------------------+-------------------------------------- I set the clouds in motion - turn up | Frank Warmerdam, warmer...@pobox.com light and sound - activate the windows | http://pobox.com/~warmerdam and watch the world go round - Rush | Geospatial Software Developer _______________________________________________ gdal-dev mailing list gdal-dev@lists.osgeo.org http://lists.osgeo.org/mailman/listinfo/gdal-dev