Provided by: grass-doc_7.6.0-1_all bug


       i.colors.enhance  - Performs auto-balancing of colors for RGB images.


       imagery, RGB, satellite, colors


       i.colors.enhance --help
       i.colors.enhance   [-fprs]  red=name  green=name  blue=name   [strength=float]    [--help]
       [--verbose]  [--quiet]  [--ui]

           Extend colors to full range of data on each channel

           Preserve relative colors, adjust brightness only

           Reset to standard color range

           Process bands serially (default: run in parallel)

           Print usage summary

           Verbose module output

           Quiet module output

           Force launching GUI dialog

       red=name [required]
           Name of red channel

       green=name [required]
           Name of green channel

       blue=name [required]
           Name of blue channel

           Cropping intensity (upper brightness level)
           Options: 0-100
           Default: 98


       i.colors.enhance auto-balances and enhances the color channels of a RGB image  (e.g.  from
       Landsat)  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

       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.


       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.


       North Carolina sample dataset example with Landsat data:
       g.region raster=lsat7_2002_10 -p
       d.rgb blue=lsat7_2002_10 green=lsat7_2002_20 red=lsat7_2002_30
       d.barscale at=55.3125,93.125 bcolor=white text_pos=over
       i.colors.enhance 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=55.3125,93.125 bcolor=white text_pos=over
       Uncorrected RGB composite of Landsat ETM channels B/G/R

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


       The strength option requires further refinement.


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


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

       Last changed: $Date: 2018-03-02 23:22:33 +0100 (Fri, 02 Mar 2018) $


       Available at: i.colors.enhance source code (history)

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