1NEARBLACK(1) GDAL NEARBLACK(1)
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6 nearblack - Convert nearly black/white borders to black.
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9 nearblack [-of format] [-white | [-color c1,c2,c3...cn]*] [-near dist] [-nb non_black_pixels]
10 [-setalpha] [-setmask] [-o outfile] [-q] [-co "NAME=VALUE"]* infile
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13 This utility will scan an image and try to set all pixels that are
14 nearly or exactly black, white or one or more custom colors around the
15 collar to black or white. This is often used to "fix up" lossy com‐
16 pressed air photos so that color pixels can be treated as transparent
17 when mosaicing. The output format must use lossless compression if ei‐
18 ther alpha band or mask band is not set.
19 -o <outfile>
21 The name of the output file to be created.
22 -of <format>
24 Select the output format. Starting with GDAL 2.3, if not speci‐
25 fied, the format is guessed from the extension (previously was
26 ERDAS Imagine .img). Use the short format name (GTiff for Geo‐
27 TIFF for example).
28 -co `"NAME=VALUE"`
30 Passes a creation option to the output format driver. Multiple
31 -co options may be listed. See Raster drivers format specific
32 documentation for legal creation options for each format.
33 Only valid when creating a new file
35 -white Search for nearly white (255) pixels instead of nearly black
37 pixels.
38 -color <c1,c2,c3...cn>
40 Search for pixels near the specified color. May be specified
41 multiple times. When -color is specified, the pixels that are
42 considered as the collar are set to 0.
43 -near <dist>
45 Select how far from black, white or custom colors the pixel val‐
46 ues can be and still considered near black, white or custom
47 color. Defaults to 15.
48 -nb <non_black_pixels>
50 number of non-black pixels that can be encountered before the
51 giving up search inwards. Defaults to 2.
52 -setalpha
54 Adds an alpha band if the output file is specified and the input
55 file has 3 bands, or sets the alpha band of the output file if
56 it is specified and the input file has 4 bands, or sets the al‐
57 pha band of the input file if it has 4 bands and no output file
58 is specified. The alpha band is set to 0 in the image collar
59 and to 255 elsewhere.
60 -setmask
62 Adds a mask band to the output file, or adds a mask band to the
63 input file if it does not already have one and no output file is
64 specified. The mask band is set to 0 in the image collar and to
65 255 elsewhere.
66 -q Suppress progress monitor and other non-error output.
68 <infile>
70 The input file. Any GDAL supported format, any number of bands,
71 normally 8bit Byte bands.
72 The algorithm processes the image one scanline at a time. A scan "in"
74 is done from either end setting pixels to black or white until at least
75 "non_black_pixels" pixels that are more than "dist" gray levels away
76 from black, white or custom colors have been encountered at which point
77 the scan stops. The nearly black, white or custom color pixels are set
78 to black or white. The algorithm also scans from top to bottom and from
79 bottom to top to identify indentations in the top or bottom.
80 The processing is all done in 8bit (Bytes).
82 If the output file is omitted, the processed results will be written
84 back to the input file - which must support update.
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87 This utility is also callable from C with GDALNearblack().
88 New in version 2.1.
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93 Frank Warmerdam <warmerdam@pobox.com>
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96 1998-2023
97 Oct 30, 2023 NEARBLACK(1)