GDAL-RASTER-CLEAN-COLLAR(1) GDAL GDAL-RASTER-CLEAN-COLLAR(1)
NAME
gdal-raster-clean-collar - Clean the collar of a raster dataset,
removing noise
Added in version 3.11.
SYNOPSIS
Usage: gdal raster clean-collar [OPTIONS] []
Clean the collar of a raster dataset, removing noise.
Positional arguments:
-i, --input Input raster dataset [required]
-o, --output Output raster dataset
Common Options:
-h, --help Display help message and exit
--json-usage Display usage as JSON document and exit
--config = Configuration option [may be repeated]
--progress Display progress bar
Options:
-f, --of, --format, --output-format Output format
--co, --creation-option = Creation option [may be repeated]
--overwrite Whether overwriting existing output is allowed
--update Whether to open existing dataset in update mode
--color Transparent color(s): tuple of integer (like 'r,g,b'), 'black', 'white' (default: black) [may be repeated]
--color-threshold Select how far from specified transparent colors the pixel values are considered transparent. (default: 15)
--pixel-distance Number of consecutive transparent pixels that can be encountered before the giving up search inwards. (default: 2)
--add-alpha Adds an alpha band to the output dataset.
Mutually exclusive with --add-mask
--add-mask Adds a mask band to the output dataset.
Mutually exclusive with --add-alpha
--algorithm Algorithm to apply. ALGORITHM=floodfill|twopasses (default: floodfill)
Advanced Options:
--oo, --open-option = Open options [may be repeated]
--if, --input-format Input formats [may be repeated]
DESCRIPTION
gdal raster clean-collar scans a (8-bit) image and sets all pixels that
are nearly or exactly black (the default), white or one or more custom
colors around the collar to black or white. This is often used to "fix
up" lossy compressed air photos so that color pixels can be treated as
transparent when mosaicing. The output format must use lossless
compression if either alpha band or mask band is not set.
Standard options
-f, --of, --format, --output-format
Which output raster format to use. Allowed values may be given
by gdal --formats | grep raster | grep + | sort
--co =
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.
--update
If only an input dataset is specified, ask for it to be opened
in update mode If an output dataset is specified, ask for it to
be opened in update mode (this implies that it already exists).
Note that updating an existing dataset may lead to file size
increase if the dataset is compressed, and/or quality loss if
lossy compression is used.
--color ,,...|black|white
Search for pixels near the specified color. May be specified
multiple times. When this option is specified, the pixels that
are considered as the collar are set to 0, unless only white is
specified, in which case there are set to 255.
--color-threshold
Select how far from black, white or custom colors the pixel
values can be and still considered near black, white or custom
color. Defaults to 15.
--pixel-distance
Number of consecutive transparent pixels that can be encountered
before the giving up search inwards. Said otherwise, the collar
will be extended by this number of pixels. Defaults to 2.
--addalpha
Adds an alpha band to the output file. The alpha band is set to
0 in the image collar and to 255 elsewhere. This option is
mutually exclusive with --addmask.
--addmask
Adds a mask band to the output file, The mask band is set to 0
in the image collar and to 255 elsewhere. This option is
mutually exclusive with --addalpha.
--algorithm floodfill|twopasses
Selects the algorithm to apply.
twopasses uses a top-to-bottom pass followed by a bottom-to-top
pass. It may miss with concave areas. The algorithm processes
the image one scanline at a time. A scan "in" is done from
either end setting pixels to black or white until at least
"non_black_pixels" pixels that are more than "dist" gray levels
away from black, white or custom colors have been encountered at
which point the scan stops. The nearly black, white or custom
color pixels are set to black or white. The algorithm also scans
from top to bottom and from bottom to top to identify
indentations in the top or bottom.
floodfill (default) uses the Flood Fill algorithm and will work
with concave areas. It requires creating a temporary dataset and
is slower than twopasses. When a non-zero value for
--pixel-distance is used, twopasses is actually called as an
initial step of floodfill.
EXAMPLES
Example 1: Edit in place a dataset using the default black color as the
color of the collar
$ gdal raster clean-collar --update my.tif
Example 2: Create a new dataset, using black or white as the color of the
collar, considering values in the [0,5] range as being considered
black, and values in the [250,255] range to be white. It also adds an
alpha band to the output dataset.
$ gdal raster clean-collar --addalpha --color=black --color=white --color-threshold=5 in.tif out.tif
AUTHOR
Even Rouault
COPYRIGHT
1998-2025
May 6, 2025 GDAL-RASTER-CLEAN-COLLAR(1)