NAME

       gdal_sieveRemoves small raster polygons.

SYNOPSIS

       gdal_sieve.py [-q] [-st threshold] [-4] [-8] [-o name=value]
                  srcfile [-nomask] [-mask filename] [-of format] [dstfile]

DESCRIPTION

       The gdal_sieve.py script removes raster polygons smaller than a provided threshold size
       (in pixels) and replaces replaces them with the pixel value of the largest neighbour
       polygon. The result can be written back to the existing raster band, or copied into a new
       file.

       The input dataset is read as integer data which means that floating point values are
       rounded to integers. Re-scaling source data may be necessary in some cases (e.g. 32-bit
       floating point data with min=0 and max=1).

       Additional details on the algorithm are available in the GDALSieveFilter() docs.

       -q:
           The script runs in quiet mode. The progress monitor is suppressed and routine messages
           are not displayed.

       -st threshold:
           Set the size threshold in pixels. Only raster polygons smaller than this size will be
           removed.

       -o name=value:
           Specify a special argument to the algorithm. Currently none are supported.

       -4:
           Four connectedness should be used when determining polygons. That is diagonal pixels
           are not considered directly connected. This is the default.

       -8:
           Eight connectedness should be used when determining polygons. That is diagonal pixels
           are considered directly connected.

       srcfile
           The source raster file used to identify target pixels. Only the first band is used.

       -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).

       dstfile
           The new file to create with the filtered result. If not provided, the source band is
           updated in place.

       -of format:
           Select the output format. Starting with GDAL 2.3, if not specified, the format is
           guessed from the extension (previously was GTiff). Use the short format name.

AUTHORS

       Frank Warmerdam warmerdam@pobox.com