NAME
r.rescale - Rescales the range of category values
in a raster map layer.
(GRASS Raster Program)
SYNOPSIS
r.rescale
r.rescale help
r.rescale [-qz]
input=name
[from=min,max]
output=name [to=min,max]
[TITLE="phrase"]
DESCRIPTION
The r.rescale program rescales the range of
category values appearing in a raster map layer. A new
raster map layer, and an appropriate category file and
color table based upon the original raster map layer, are
generated with category labels that reflect the original
category values that produced each category. This command
is useful for producing representations with a reduced
number of categories from a raster map layer with a large
range of category values (e.g., elevation).
Rescaled map layers are appropriate for use in
such GRASS programs as
r.stats,
r.report, and
r.coin.
OPTIONS
r.rescale will be run non-interactively if the
user specifies program arguments on the command line, using
the form:
r.rescale [-qz] input=name
[from=min,max] output=name
[to=min,max] [TITLE="phrase"]
Alternately, the user can simply type:
-
r.rescale
on the command line without program arguments. In this
case, the user will be prompted for parameter values using
the standard GRASS user interface described in the manual
entry for
parser.
Flag:
- -q
- Run quietly, without printing messages on program
progress to the user's terminal.
- -z
- Use zero (0) for transparency instead of NULL, that means
set values outside range to zero (0) instead of NULL.
Parameters:
- input=name
- The name of the raster map layer whose category values
are to be rescaled.
- from=min,max
- The input map range to be rescaled.
Default: The full range of the input map layer.
- output=name
- The name of the new, rescaled raster map layer.
- to=min,max
- The output map range (after rescaling).
Default: 1,255
- TITLE="phrase"
- Title for new output raster map layer.
EXAMPLE
To rescale an elevation raster map layer with category
values ranging from 1090 meters to 1800 meters into the
range 1-255, the following command line could be used:
-
r.rescale input=elevation from=1090,1800 output=elevation.255 to=1,255
NOTES
The rescaled category value range is actually unlimited,
but the category value range 1 to 255 is frequently used
due to limitations of color graphics monitors.
Category values that fall beyond the input range will
become NULL. This allows the user to select a subset of
the full category value range for rescaling if desired.
This also means that the user should know the category
value range for the input raster map layer. The user can
request the r.rescale program to determine
this range, or can obtain it using the
r.describe
command. If the category value range is determined using
r.rescale, the input raster map layer is examined,
and the minimum and maximum non-NULL category values are
selected as the input range.
SEE ALSO
r.coin,
r.describe,
r.mapcalc,
r.reclass,
r.report,
r.resample,
r.stats,
and
parser
AUTHOR
Michael Shapiro,
U.S.Army Construction Engineering
Research Laboratory