r.his(1grass) GRASS GIS User's Manual r.his(1grass)
NAME
r.his - Generates red, green and blue (RGB) raster map layers combin-
ing hue, intensity and saturation (HIS) values from user-specified in-
put raster map layers.
KEYWORDS
raster, color transformation, RGB, HIS, IHS
SYNOPSIS
r.his
r.his --help
r.his [-c] hue=string [intensity=string] [saturation=string]
red=string green=string blue=string [bgcolor=name] [--overwrite]
[--help] [--verbose] [--quiet] [--ui]
Flags:
-c
Use colors from color tables for NULL values
--overwrite
Allow output files to overwrite existing files
--help
Print usage summary
--verbose
Verbose module output
--quiet
Quiet module output
--ui
Force launching GUI dialog
Parameters:
hue=string [required]
Name of layer to be used for hue
intensity=string
Name of layer to be used for intensity
saturation=string
Name of layer to be used for saturation
red=string [required]
Name of output layer to be used for red
green=string [required]
Name of output layer to be used for green
blue=string [required]
Name of output layer to be used for blue
bgcolor=name
Color to use instead of NULL values
Either a standard color name, R:G:B triplet, or "none"
DESCRIPTION
HIS stands for hue, intensity, and saturation. This program produces
red, green and blue raster map layers providing a visually pleasing
combination of hue, intensity, and saturation values from two or three
user-specified raster map layers.
The human brain automatically interprets the vast amount of visual in-
formation available according to basic rules. Color, or hue, is used
to categorize objects. Shading, or intensity, is interpreted as
three-dimensional texturing. Finally, the degree of haziness, or satu-
ration, is associated with distance or depth. This program allows data
from up to three raster map layers to be combined into a color image
(in the form of separate red, green and blue raster map layers) which
retains the original information in terms of hue, intensity, and satu-
ration.
While any raster map layer can be used to represent the hue informa-
tion, map layers with a few very distinct colors work best. Only
raster map layers representing continuously varying data like eleva-
tion, aspect, weights, intensities, or amounts can suitably be used to
provide intensity and saturation information.
For example, a visually pleasing image can be made by using a watershed
map for the hue factor, an aspect map for the intensity factor, and an
elevation map for saturation. (The user may wish to leave out the ele-
vation information for a first try.) Ideally, the resulting image
should resemble the view from an aircraft looking at a terrain on a
sunny day with a bit of haze in the valleys.
The Process
Each map cell is processed individually. First, the working color is
set to the color of the corresponding cell in the map layer chosen to
represent hue. Second, this color is multiplied by the red intensity
of that cell in the intensity map layer. This map layer should have an
appropriate gray-scale color table associated with it. You can ensure
this by using the color manipulation capabilities of r.colors. Fi-
nally, the color is made somewhat gray-based on the red intensity of
that cell in the saturation map layer. Again, this map layer should
have a gray-scale color table associated with it.
NOTES
The name is misleading. The actual conversion used is
H.i.s + G.(1-s)
where
H is the R,G,B color from the hue map
i is the red value from the intensity map
s is the red value from the saturation map
G is 50% gray (R = G = B = 0.5)
Either (but not both) of the intensity or the saturation map layers may
be omitted. This means that it is possible to produce output images
that represent combinations of his, hi, or hs. The separate red, green
and blue maps can be displayed on the graphics monitor using d.rgb, or
combined into a composite RGB layer using r.composite. Users wishing
to simply display an his composite image without actually generating
any layers should use the program d.his.
EXAMPLES
Recreate the following example for d.his using r.his. First, create
shaded relief and show it.
g.region raster=elevation
r.relief input=elevation output=elevation_shaded_relief
d.mon wx0
d.his hue=elevation intensity=elevation_shaded_relief brighten=50
Second, compute lighter version of color of shaded relief. Then con-
vert from HIS model to RGB and show the result.
r.mapcalc "elevation_shaded_relief_bright_50 = #elevation_shaded_relief * 1.5"
r.colors elevation_shaded_relief_bright_50 color=grey255
r.his hue=elevation intensity=elevation_shaded_relief_bright_50 \
red=shadedmap_r green=shadedmap_g blue=shadedmap_b
d.mon wx1
d.rgb red=shadedmap_r green=shadedmap_g blue=shadedmap_b
SEE ALSO
d.his, d.colortable, d.rgb, r.blend, r.colors, r.composite, r.mapcalc,
r.shade, i.his.rgb, i.rgb.his
AUTHOR
Glynn Clements (based upon d.his)
SOURCE CODE
Available at: r.his source code (history)
Accessed: unknown
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GRASS 7.8.7 r.his(1grass)
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