GDAL-RASTER-SIEVE(1)                 GDAL                 GDAL-RASTER-SIEVE(1)

NAME
       gdal-raster-sieve - Remove small raster polygons

       Added in version 3.11.


SYNOPSIS

          Usage: gdal raster sieve [OPTIONS] <INPUT> <OUTPUT>

          Remove small polygons from a raster dataset.

          Positional arguments:
            -i, --input <INPUT>                                  Input raster dataset [required]
            -o, --output <OUTPUT>                                Output raster dataset (created by algorithm) [required]

          Common Options:
            -h, --help                                           Display help message and exit
            --json-usage                                         Display usage as JSON document and exit
            --config <KEY>=<VALUE>                               Configuration option [may be repeated]
            --progress                                           Display progress bar

          Options:
            -f, --of, --format, --output-format <OUTPUT-FORMAT>  Output format
            --co, --creation-option <KEY>=<VALUE>                Creation option [may be repeated]
            --overwrite                                          Whether overwriting existing output is allowed
            --mask <MASK>                                        Use the first band of the specified file as a validity mask (all pixels with a value other than zero will be considered suitable for inclusion in polygons)
            -b, --band <BAND>                                    Input band (1-based index)
            -s, --size-threshold <SIZE-THRESHOLD>                Minimum size of polygons to keep (default: 2)
            -c, --connect-diagonal-pixels                        Consider diagonal pixels as connected

          Advanced Options:
            --oo, --open-option <KEY>=<VALUE>                    Open options [may be repeated]
            --if, --input-format <INPUT-FORMAT>                  Input formats [may be repeated]

DESCRIPTION
       gdal raster sieve removes raster polygons smaller than a provided
       threshold size (in pixels) and replaces them with the pixel value of
       the largest neighbour polygon.

       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).

   Standard options

       -f, --of, --format, --output-format <OUTPUT-FORMAT>
              Which output raster format to use. Allowed values may be given
              by gdal --formats | grep raster | grep rw | sort

       --co <NAME>=<VALUE>
              Many formats have one or more optional creation options that can
              be used to control particulars about the file created. For
              instance, the GeoTIFF driver supports creation options to
              control compression, and whether the file should be tiled.

              May be repeated.

              The creation options available vary by format driver, and some
              simple formats have no creation options at all. A list of
              options supported for a format can be listed with the --formats
              command line option but the documentation for the format is the
              definitive source of information on driver creation options.
              See Raster drivers format specific documentation for legal
              creation options for each format.

       --overwrite
              Allow program to overwrite existing target file or dataset.
              Otherwise, by default, gdal errors out if the target file or
              dataset already exists.

       -b, --band <BAND>
              Input band (1-based index)

       -s, --size-threshold <SIZE-THRESHOLD>
              Minimum size of polygons to keep (default: 2)

       -c, --connect-diagonal-pixels
              Consider diagonal pixels (pixels at the corners) as connected.
              The default behavior is to only consider pixels that are
              touching the edges as connected, which is the same as
              4-connectivity. When this option is selected, the algorithm will
              also consider pixels at the corners as connected, which is the
              same as 8-connectivity.

       --mask <MASK>
              Use the first band of the specified file as a validity mask: all
              pixels in the mask band with a value other than zero will be
              considered suitable for inclusion in polygons.

EXAMPLES
   Example 1: Remove polygons smaller than 10 pixels from the band 2 of a
       raster.

          $ gdal raster sieve -b 2 -s 10 input.tif output.tif

AUTHOR
       Alessandro Pasotti <elpaso@itopen.it>

COPYRIGHT
       1998-2025

                                  May 6, 2025             GDAL-RASTER-SIEVE(1)