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


       raster, color transformation


       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]

           Respect NULL values while drawing

           Allow output files to overwrite existing files

           Verbose module output

           Quiet module output

           Name of layer to be used for HUE

           Name of layer to be used for INTENSITY

           Name of layer to be used for SATURATION

           Name of output layer to be used for RED

           Name of output layer to be used for GREEN

           Name of output layer to be used for BLUE


       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.


       The name is misleading. The actual conversion used is
         <u>H.i.s + <u>G.(1-s)
         <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.


       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
         d.rgb red=esr.r green=esr.g blue=esr.b


       d.his, d.colors, d.colortable, d.rgb, r.blend, r.colors, r.composite i.his.rgb, i.rgb.his


       Glynn Clements (based upon d.his)

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

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