gdal_polygonize - Produces a polygon feature layer from a
raster.
gdal_polygonize.py [-8] [-nomask] [-mask filename] <raster_file> [-b band]
[-q] [-f ogr_format] <out_file> [layer] [fieldname]
This utility creates vector polygons for all connected regions of
pixels in the raster sharing a common pixel value. Each polygon is created
with an attribute indicating the pixel value of that polygon. A raster mask
may also be provided to determine which pixels are eligible for
processing.
The utility will create the output vector datasource if it does
not already exist, defaulting to GML format.
The utility is based on the :GDALPolygonize() function
which has additional details on the algorithm.
- -8
- Use 8 connectedness. Default is 4 connectedness.
- -nomask
- Do not use the default validity mask for the input band (such as nodata,
or alpha masks).
- -mask
<filename>
- Use the first band of the specified file as a validity mask (zero is
invalid, non-zero is valid). If not specified, the default validity mask
for the input band (such as nodata, or alpha masks) will be used (unless
-nomask is specified)
- <raster_file>
- The source raster file from which polygons are derived.
- -b <band>
- The band on <raster_file> to build the polygons from. Starting with
GDAL 2.2, the value can also be set to "mask", to indicate that
the mask band of the first band must be used (or
"mask,band_number" for the mask of a specified band)
- -f
<ogr_format>
- Select the output format. Starting with GDAL 2.3, if not specified, the
format is guessed from the extension (previously was GML). Use the short
format name
- <out_file>
- The destination vector file to which the polygons will be written.
- <layer>
- The name of the layer created to hold the polygon features.
- <fieldname>
- The name of the field to create (defaults to "DN").
- -q
- The script runs in quiet mode. The progress monitor is suppressed and
routine messages are not displayed.
Frank Warmerdam <warmerdam@pobox.com>