Then, you can run a separate command to process the non-alpha bands. You need two processes because there may not be one-to-one mapping of the non-alpha and alpha band polygons.
Finally, you need to make intersections of the polygons in the two layers and store the values of the alpha band polygons. I can't find any scripts that do this. I'm afraid you need to do this yourselves. On Tue, Jul 26, 2011 at 9:56 AM, Chaitanya kumar CH <chaitanya...@gmail.com>wrote: > John, > > gdal_polygonize script stores the common pixel value in a field for every > polygon. By default it is named 'DN', which can be changed by specifying the > fieldname option. > > You must use the alpha channel to polygonize. So you have to use the -b > option to specify that and may have to use the -nomask option too. > > > On Tue, Jul 26, 2011 at 9:21 AM, jt2000 <thak...@nexgenwireless.com>wrote: > >> Thanks Jay, >> >> Ideally I would like the data to be in a column of the shapefile output so >> I >> can load it in the database and use it to query. With gdal_polygonize.py >> this doesn't seem possible so I was wondering what other options are out >> there. >> >> -- >> View this message in context: >> http://osgeo-org.1803224.n2.nabble.com/preserving-alpha-channel-data-with-gdal-transform-py-tp6620877p6620923.html >> Sent from the GDAL - Dev mailing list archive at Nabble.com. >> _______________________________________________ >> gdal-dev mailing list >> gdal-dev@lists.osgeo.org >> http://lists.osgeo.org/mailman/listinfo/gdal-dev >> > > > > -- > Best regards, > Chaitanya kumar CH. > > +91-9494447584 > 17.2416N 80.1426E > -- Best regards, Chaitanya kumar CH. +91-9494447584 17.2416N 80.1426E
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