## NAME

i.landsat.rgb - Auto-balancing of colors for LANDSAT images

## KEYWORDS

raster, imagery, colors

## SYNOPSIS

i.landsat.rgb
i.landsat.rgb help
i.landsat.rgb [-fpr] red=string green=string blue=string [strength=integer]

### Flags:

-f
  Extend colors to full range of data on each channel
-p
  Preserve relative colors, adjust brightness only
-r
  Reset to standard color range

### Parameters:

red=string
  LANDSAT red channel
green=string
  LANDSAT green channel
blue=string
  LANDSAT blue channel
strength=integer
  Cropping intensity (upper brightness level)
  Options: 0-100
  Default: 98

## DESCRIPTION

i.landsat.rgb auto-balances and enhances the color channels of a LANDSAT RGB image to provide a more natural color mixture. Only the color table of each image band is modified, the base data remains untouched.

The module works by calculating a histogram for each color channel and removing an adjustable amount of outliers from either end before recalibrating the color scale with r.colors.

It will work with any 8-bit RGB imagery set and the script is easily modified to work with other datasets of greater band-depth.

## NOTES

Depending on the image, it may or may not be advantageous to use the -p flag to preserve the relative color scaling. You will have to experiment with the different options to find a setting that works best for your particular imagery.

The strength option should generally be set in the 90-99 range. The lower the number, the more saturated the image becomes. It represents the percentage cut-off for the top end of the color histogram curve. The lower end is fixed at 2% of the area under the curve.

For quicker execution of this module on large images you can achieve largely similar results by switching to a coarser resolution before the running of the module (using g.region) and then back to the original resolution afterwards.

## TODO

The strength option requires further refinement.

Update to use r.univar instead of r.univar.sh once r.univar receives extended statistics support.

## SEE ALSO

d.rgb, g.region, i.oif, r.colors, r.composite, r.univar, r.univar.sh

## AUTHORS

Markus Neteler
M. Hamish Bowman, Dept. Marine Science, Otago University, New Zealand

Last changed: $Date: 2006/04/19 06:51:32 $

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