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

NAME

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

KEYWORDS

       raster, color transformation

SYNOPSIS

       r.his
       r.his help
       r.his  [-n]  h_map=string   [i_map=string]    [s_map=string]   r_map=string   g_map=string   b_map=string
       [--overwrite]  [--verbose]  [--quiet]

   Flags:
       -n
           Respect NULL values while drawing

       --overwrite
           Allow output files to overwrite existing files

       --verbose
           Verbose module output

       --quiet
           Quiet module output

   Parameters:
       h_map=string
           Name of layer to be used for HUE

       i_map=string
           Name of layer to be used for INTENSITY

       s_map=string
           Name of layer to be used for SATURATION

       r_map=string
           Name of output layer to be used for RED

       g_map=string
           Name of output layer to be used for GREEN

       b_map=string
           Name of output layer to be used for BLUE

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
d.colors or 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
         <u>H.i.s + <u>G.(1-s)
       where
         <u>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
         <u>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.

EXAMPLE

       Recreate the following d.his command using r.his:
         r.shaded.relief map=elevation.dem shad=elev.shad_relf
         d.his h=elevation.dem i=elev.shad_relf brighten=50

         r.mapcalc 'elev.shad_relf_bright50 = #elev.shad_relf * 1.5'
         r.colors elev.shad_relf_bright50 color=grey255
         r.his h_map=elevation.dem i_map=elev.shad_relf_bright50 r_map=esr.r g_map=esr.g bmap=esr.b
         d.rgb red=esr.r green=esr.g blue=esr.b

AUTHOR

       Glynn Clements (based upon d.his)

       Last changed: $Date: 2008-05-16 10:02:53 -0700 (Fri, 16 May 2008) $

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       © 2003-2013 GRASS Development Team

GRASS 6.4.3                                                                                        r.his(1grass)