r.rescale.eq - GRASS GIS manual
Author: GRASS Development Team
Description: r.rescale.eq: Rescales histogram equalized the range of category values in a raster map layer.
Keywords: raster, rescale

## NAME

r.rescale.eq - Rescales histogram equalized the range of category values in a raster map layer.

## KEYWORDS

raster, rescale

## SYNOPSIS

r.rescale.eq
r.rescale.eq --help
r.rescale.eq input=name [from=min,max] output=name to=min,max [title=phrase] [--overwrite] [--help] [--verbose] [--quiet] [--ui]

### Flags:

--overwrite
  Allow output files to overwrite existing files
--help
  Print usage summary
--verbose
  Verbose module output
--quiet
  Quiet module output
--ui
  Force launching GUI dialog

### Parameters:

input=name [required]
  The name of the raster map to be rescaled
from=min,max
  The input data range to be rescaled (default: full range of input map)
output=name [required]
  The resulting raster map name
to=min,max [required]
  The output data range
title=phrase
  Title for new raster map

## DESCRIPTION

The r.rescale.eq program rescales the range of category values appearing in a raster map layer with equalized histogram. 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 GIS commands as r.stats, r.report, and r.coin.

## EXAMPLE

To rescale an elevation raster map layer with category values ranging from 1090 meters to 1800 meters into the range 0-255, the following command line could be used (without the from parameter, the full value range will be used):

    r.rescale.eq input=elevation from=1090,1800 output=elevation.255 to=0,255

## NOTES

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.eq program to determine this range, or can obtain it using the r.describe or r.info command. If the category value range is determined using r.rescale.eq, 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.info, r.mapcalc, r.reclass, r.rescale, r.report, r.resample, r.stats

## AUTHOR

Michael Shapiro, U.S.Army Construction Engineering Research Laboratory

## SOURCE CODE

Available at: r.rescale.eq source code (history)

Accessed: Sunday Jun 21 14:58:50 2026

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© 2003-2023 GRASS Development Team, GRASS GIS 7.8.8 Reference Manual