NAME
i.landsat.rgb - 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=integer] [--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=integer
- 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
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 02:24:10 -0700 (Thu, 07 Sep 2006) $
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