## NAME

i.landsat.rgb

## 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.

## EXAMPLE

    i.landsat.rgb red=tm.3 green=tm.2 blue=tm.1

## TODO

The strength option requires further refinement.

## SEE ALSO

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

## AUTHORS

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

Last changed: $Date: 2006-09-07 11:24:10 +0200 (Thu, 07 Sep 2006) $

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