nearblack

Description

R wrapper for nearblack: convert nearly black/white borders to black

Usage

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nearblack(infile, o, of, co, white, color, near, nb, setalpha, setmask, q,
  output_Raster = FALSE, overwrite = FALSE, ignore.full_scan = TRUE,
  verbose = FALSE)

Arguments

infile

Character. The input file. Any GDAL supported format, any number of bands, normally 8bit Byte bands.

o

Character. outfile. The name of the output file to be created. Newly created files are created with the HFA driver by default (Erdas Imagine - .img)

of

Character. format. (GDAL 1.8.0 or later) Select the output format. Use the short format name (GTiff for GeoTIFF for example).

co

Character. "NAME=VALUE". (GDAL 1.8.0 or later) Passes a creation option to the output format driver. Multiple -co options may be listed. See format specific documentation for legal creation options for each format. Only valid when creating a new file.

white

Logical. Search for nearly white (255) pixels instead of nearly black pixels.

color

Numeric. c1,c2,c3...cn. (GDAL >= 1.9.0) Search for pixels near the specified color. May be specified multiple times. When -color is specified, the pixels that are considered as the collar are set to 0.

near

Numeric. dist. 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.

nb

Numeric. non_black_pixels. number of non-black pixels that can be encountered before the giving up search inwards. Defaults to 2.

setalpha

Logical. (GDAL 1.8.0 or later) Adds an alpha band if the output file is specified and the input file has 3 bands, or sets the alpha band of the output file if it is specified and the input file has 4 bands, or sets the alpha band of the input file if it has 4 bands and no output file is specified. The alpha band is set to 0 in the image collar and to 255 elsewhere.

setmask

Logical. (GDAL 1.8.0 or later) Adds a mask band to the output file, or adds a mask band to the input file if it does not already have one and no output file is specified. The mask band is set to 0 in the image collar and to 255 elsewhere.

q

Logical. (GDAL 1.8.0 or later) Suppress progress monitor and other non-error output.

output_Raster

Logical. Return outfile as a RasterBrick?

overwrite

Logical. If output file exists, OR if output file is not set (which would defualt to overwriting the input file), allow overwriting?

ignore.full_scan

Logical. If FALSE, perform a brute-force scan if other installs are not found. Default is TRUE.

verbose

Logical. Enable verbose execution? Default is FALSE.

Details

#' This is an R wrapper for the 'nearblack' function that is part of the Geospatial Data Abstraction Library (GDAL). It follows the parameter naming conventions of the original function, with some modifications to allow for more R-like parameters. For all parameters, the user can use a single character string following, precisely, the gdalinfo format (http://gdal.org/nearblack.html), or, in some cases, can use R vectors to achieve the same end.

This utility will scan an image and try to set all pixels that are nearly or exactly black, white or one or more custom colors around the collar to black or white. This is often used to "fix up" lossy compressed airphotos so that color pixels can be treated as transparent when mosaicking.

This function assumes the user has a working GDAL on their system. If the "gdalUtils_gdalPath" option has been set (usually by gdal_setInstallation), the GDAL found in that path will be used. If nothing is found, gdal_setInstallation will be executed to attempt to find a working GDAL.

Author(s)

Jonathan A. Greenberg (gdalUtils@estarcion.net) (wrapper) and Frank Warmerdam (GDAL lead developer).

References

http://www.gdal.org/nearblack.html

Examples

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# None available at present.