.TH "gdal_polygonize" 1 "Fri Mar 22 2019" "GDAL" \" -*- nroff -*-
.ad l
.nh
.SH NAME
gdal_polygonize \- Produces a polygon feature layer from a raster\&.
.SH "SYNOPSIS"
.PP
.PP
.nf
gdal_polygonize.py [-8] [-nomask] [-mask filename] raster_file [-b band]
                [-q] [-f ogr_format] out_file [layer] [fieldname]
.fi
.PP
.SH "DESCRIPTION"
.PP
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\&.
.PP
The utility will create the output vector datasource if it does not already exist, defaulting to GML format\&.
.PP
The utility is based on the GDALPolygonize() function which has additional details on the algorithm\&.
.PP
.IP "\fB\fB-8\fP:\fP" 1c
(GDAL >= 1\&.10) Use 8 connectedness\&. Default is 4 connectedness\&. 
.PP
.IP "\fB\fB-nomask\fP:\fP" 1c
Do not use the default validity mask for the input band (such as nodata, or alpha masks)\&. 
.PP
.IP "\fB\fB-mask\fP \fIfilename\fP:\fP" 1c
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) 
.PP
.IP "\fB\fIraster_file\fP\fP" 1c
The source raster file from which polygons are derived\&.
.PP
.IP "\fB\fB-b\fP \fIband\fP: \fP" 1c
The band on \fIraster_file\fP 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) 
.PP
.IP "\fB\fB-f\fP \fIogr_format\fP\fP" 1c
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 
.PP
.IP "\fB\fIout_file\fP\fP" 1c
The destination vector file to which the polygons will be written\&. 
.PP
.IP "\fB\fIlayer\fP\fP" 1c
The name of the layer created to hold the polygon features\&. 
.PP
.IP "\fB\fIfieldname\fP\fP" 1c
The name of the field to create (defaults to 'DN')\&. 
.PP
.IP "\fB\fB-q\fP:\fP" 1c
The script runs in quiet mode\&. The progress monitor is suppressed and routine messages are not displayed\&. 
.PP
.PP
.PP
.SH "AUTHORS"
.PP
Frank Warmerdam warmerdam@pobox.com