Hi all,<br>
<br>
I was writing to enquire about the status of the "8CONNECTED=8" option in
the Polygonize function of GDAL 1.8. I would expect that this option
joins all pixels of equal value that are diagonally adjacent into a
single polygon.<br>
<br>
However, with the following raster dataset (see
<a href="http://i.imgur.com/jdUla.png">http://i.imgur.com/jdUla.png</a> ) I receive two polygons in my output
shapefile (see <a href="http://i.imgur.com/CZWMU.png">http://i.imgur.com/CZWMU.png</a> ). For a copy of the
raster, see <a href="http://dl.dropbox.com/u/6732375/mish9000.img.zip">http://dl.dropbox.com/u/6732375/mish9000.img.zip</a> I am
calling polygonize from GDAL's python bindings, which reports itself as
"GDAL 1.8.0, released 2011/01/12". My code looks like: <br>
<br>
<blockquote>gdal.Polygonize(tmprasterband, tmprasterband, shapefile_polygons_layer, 0, ["8CONNECTED=8"])<br>
</blockquote>
<br>
Is this the expected behaviour or a bug? Can I modify my call to
polygonize to get the desired behaviour? If not, how would I merge
multiple polygons with the same attribute value (an id number) into a
single geometry?<br>
<br>
Thanks for your help,<br>
<br>
Francis Markham