NAME

       d.rgb  - Displays three user-specified raster maps as red, green, and blue overlays in the
       active graphics frame.

KEYWORDS

       display, graphics, raster, RGB

SYNOPSIS

       d.rgb
       d.rgb --help
       d.rgb [-n] red=name green=name blue=name  [--help]  [--verbose]  [--quiet]  [--ui]

   Flags:
       -n
           Make null cells opaque

       --help
           Print usage summary

       --verbose
           Verbose module output

       --quiet
           Quiet module output

       --ui
           Force launching GUI dialog

   Parameters:
       red=name [required]
           Name of raster map to be used for <red>

       green=name [required]
           Name of raster map to be used for <green>

       blue=name [required]
           Name of raster map to be used for <blue>

DESCRIPTION

       RGB stands for red, green, and blue. d.rgb visually combines three raster maps to  form  a
       color  image.  For  each  map, the corresponding component from the layer’s color table is
       used (e.g. for the red layer, the red component is used, and so on). In general, the input
       raster maps should use a grey-scale color table.

NOTES

       d.rgb  does  not attempt to quantize the combined image into a fixed number of colors. Nor
       does it have an option to generate a composite layer  (see  r.composite  for  that).   The
       image  and  raster  maps  will not display properly if the graphics device does not have a
       reasonable sampling of the RGB color-space.

       If  color  quality  of  satellite  image  color  composites  seems  to  appear  poor,  run
       i.colors.enhance on the selected satellite channels.

       An alternative is the assignment of grey color tables to each band with r.colors:
       r.info -r image.1
       min=0
       max=255
       r.colors map=image.1 color=grey
       r.colors map=image.2 rast=image.1
       r.colors map=image.3 rast=image.1

       To write out the color composite to a combined R/G/B raster maps, use r.composite.

EXAMPLE

       Visual color composite of a LANDSAT scene (North Carolina sample dataset):
       g.region raster=lsat7_2002_10 -p
       d.rgb blue=lsat7_2002_10 green=lsat7_2002_20 red=lsat7_2002_30

SEE ALSO

        d.colortable, d.his, r.blend, r.mapcalc, r.colors, r.composite

AUTHOR

       Glynn Clements

       Last changed: $Date: 2014-12-28 16:45:01 +0100 (Sun, 28 Dec 2014) $

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