Ubuntu Manpage: r.his - Generates red, green and blue (RGB) raster map layers combining hue, intensity and saturation

Provided by: grass-doc_7.8.2-1build3_all

NAME

       r.his   -  Generates  red, green and blue (RGB) raster map layers combining hue, intensity and saturation
       (HIS) values from user-specified input 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 information 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 saturation, 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 saturation.

While any raster map layer can be used to represent the hue information, map layers with a few very
distinct colors work best. Only raster map layers representing continuously varying data like elevation,
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
elevation 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. Finally, 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 convert 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

AUTHOR

       Glynn Clements (based upon d.his)

SOURCE CODE

       Available at: r.his source code (history)

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       © 2003-2019 GRASS Development Team, GRASS GIS 7.8.2 Reference Manual