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 17:19:58 +0100 (Mon, 13 Feb 2012) $
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