1i.colors.enhance(1)         GRASS GIS User's Manual        i.colors.enhance(1)
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NAME

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

9       imagery, RGB, satellite, colors
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SYNOPSIS

12       i.colors.enhance
13       i.colors.enhance --help
14       i.colors.enhance      [-fprs]     red=name     green=name     blue=name
15       [strength=float]   [--help]  [--verbose]  [--quiet]  [--ui]
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17   Flags:
18       -f
19           Extend colors to full range of data on each channel
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21       -p
22           Preserve relative colors, adjust brightness only
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24       -r
25           Reset to standard color range
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27       -s
28           Process bands serially (default: run in parallel)
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30       --help
31           Print usage summary
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33       --verbose
34           Verbose module output
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36       --quiet
37           Quiet module output
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39       --ui
40           Force launching GUI dialog
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42   Parameters:
43       red=name [required]
44           Name of red channel
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46       green=name [required]
47           Name of green channel
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49       blue=name [required]
50           Name of blue channel
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52       strength=float
53           Cropping intensity (upper brightness level)
54           Options: 0-100
55           Default: 98
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DESCRIPTION

58       i.colors.enhance auto-balances and enhances the color channels of a RGB
59       image (e.g. from Landsat) to provide a more natural color mixture. Only
60       the color table of each image band is modified, the base  data  remains
61       untouched.
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63       The  module works by calculating a histogram for each color channel and
64       removing an adjustable amount of outliers from either end before recal‐
65       ibrating the color scale with r.colors.
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67       It  will  work  with any 8-bit RGB imagery set and the script is easily
68       modified to work with other datasets of greater band-depth.
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NOTES

71       Depending on the image, it may or may not be advantageous to use the -p
72       flag  to  preserve the relative color scaling. You will have to experi‐
73       ment with the different options to find a setting that works  best  for
74       your particular imagery.
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76       The  strength  option  should  generally be set in the 90-99 range. The
77       lower the number, the more saturated the image becomes.  It  represents
78       the  percentage  cut-off  for the top end of the color histogram curve.
79       The lower end is fixed at 2% of the area under the curve.
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81       For quicker execution of this module on large images  you  can  achieve
82       largely similar results by switching to a coarser resolution before the
83       running of the module (using g.region) and then back  to  the  original
84       resolution afterwards.
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EXAMPLE

87       North Carolina sample dataset example with Landsat data:
88       g.region raster=lsat7_2002_10 -p
89       d.rgb blue=lsat7_2002_10 green=lsat7_2002_20 red=lsat7_2002_30
90       d.barscale at=55.3125,93.125 bcolor=white text_pos=over
91       i.colors.enhance blue=lsat7_2002_10 green=lsat7_2002_20 red=lsat7_2002_30 strength=95
92       d.rgb blue=lsat7_2002_10 green=lsat7_2002_20 red=lsat7_2002_30
93       d.barscale at=55.3125,93.125 bcolor=white text_pos=over
94       Uncorrected RGB composite of Landsat ETM channels B/G/R
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96       Color corrected RGB composite of Landsat ETM channels B/G/R
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TODO

99       The strength option requires further refinement.
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SEE ALSO

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

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

109       Available at: i.colors.enhance source code (history)
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111       Accessed: Saturday Jan 21 20:41:00 2023
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113       Main  index | Imagery index | Topics index | Keywords index | Graphical
114       index | Full index
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116       © 2003-2023 GRASS Development Team, GRASS GIS 8.2.1 Reference Manual
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120GRASS 8.2.1                                                i.colors.enhance(1)