.TH "gdal_sieve" 1 "Fri Mar 22 2019" "GDAL" \" -*- nroff -*-
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.SH NAME
gdal_sieve \- Removes small raster polygons\&.
.SH "SYNOPSIS"
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.nf
gdal_sieve.py [-q] [-st threshold] [-4] [-8] [-o name=value]
           srcfile [-nomask] [-mask filename] [-of format] [dstfile]
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.SH "DESCRIPTION"
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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\&.
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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)\&.
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Additional details on the algorithm are available in the GDALSieveFilter() docs\&.
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.IP "\fB\fB-q\fP:\fP" 1c
The script runs in quiet mode\&. The progress monitor is suppressed and routine messages are not displayed\&.
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.IP "\fB\fB-st\fP \fIthreshold\fP:\fP" 1c
Set the size threshold in pixels\&. Only raster polygons smaller than this size will be removed\&.
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.IP "\fB\fB-o\fP \fIname=value\fP:\fP" 1c
Specify a special argument to the algorithm\&. Currently none are supported\&. 
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.IP "\fB\fB-4\fP:\fP" 1c
Four connectedness should be used when determining polygons\&. That is diagonal pixels are not considered directly connected\&. This is the default\&. 
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.IP "\fB\fB-8\fP:\fP" 1c
Eight connectedness should be used when determining polygons\&. That is diagonal pixels are considered directly connected\&. 
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.IP "\fB\fIsrcfile\fP\fP" 1c
The source raster file used to identify target pixels\&. Only the first band is used\&.
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.IP "\fB\fB-nomask\fP:\fP" 1c
Do not use the default validity mask for the input band (such as nodata, or alpha masks)\&. 
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.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)\&. 
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.IP "\fB\fIdstfile\fP\fP" 1c
The new file to create with the filtered result\&. If not provided, the source band is updated in place\&.
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.IP "\fB\fB-of\fP \fIformat\fP:\fP" 1c
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\&. 
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.SH "AUTHORS"
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Frank Warmerdam warmerdam@pobox.com