NAME

       i.landsat.rgb  - Performs 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=float]   [--verbose]  [--quiet]

   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

       --verbose
           Verbose module output

       --quiet
           Quiet module output

   Parameters:
       red=string
           LANDSAT red channel

       green=string
           LANDSAT green channel

       blue=string
           LANDSAT blue channel

       strength=float
           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.

EXAMPLE

       North Carolina sample dataset example:
       g.region rast=lsat7_2002_10 -p
       d.rgb blue=lsat7_2002_10 green=lsat7_2002_20 red=lsat7_2002_30
       d.barscale at=55.312500,93.125000 bcolor=white tcolor=black -t
       i.landsat.rgb blue=lsat7_2002_10 green=lsat7_2002_20 red=lsat7_2002_30 strength=95
       d.rgb blue=lsat7_2002_10 green=lsat7_2002_20 red=lsat7_2002_30
       d.barscale at=55.312500,93.125000 bcolor=white tcolor=black -t
        Uncorrected RGB composite of Landsat ETM channels B/G/R

       Color corrected RGB composite of Landsat ETM channels B/G/R

TODO

       The strength option requires further refinement.

SEE ALSO

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

AUTHORS

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

       Last changed: $Date: 2012-02-13 08:19:58 -0800 (Mon, 13 Feb 2012) $

       Full index

       © 2003-2013 GRASS Development Team

GRASS 6.4.3                                                                                i.landsat.rgb(1grass)