NAME

i.composite - An imagery function that creates a color composite image from three imagery band files specified by the user.
(GRASS Image Processing Program)

SYNOPSIS

i.composite

DESCRIPTION

i.composite creates a color composite image from three band files specified by the user. The user specifies the bands to be used by assigning a red, blue, and/or green color to each band. The resulting image is a raster map layer of raw spectral data composed of the three bands chosen by the user. The color composite can then be displayed, painted, or manipulated as would any raster map layer in GRASS.

The first prompt asks the user for the imagery group whose files are to be used.

The following menu is then displayed: 

Please indicate which files to use for red, green, and blue
colors.  You may leave any color out.  You may specify more
than one color per file.  However, each color may only be
specified once.  For example, to get a full color image,
specify r,g,b for 3 different files.  To get a grey scale
image, specify rgb for a single file.

                     b__    spot.1
                     g__    spot.2
                     r__    spot.3
                     ___    spotclass
                     ___    spotreject

    AFTER COMPLETING ALL ANSWERS, HIT <ESC> TO CONTINUE
                  (OR <Ctrl-C> TO CANCEL)
The user is then allowed to check the choice of bands: 
               Colors assigned as follows:

                 RED:     spot.3@mapsetname
                 GREEN:   spot.2@mapsetname
                 BLUE:    spot.1@mapsetname

                     Look ok? (y/n) [y]
The color table that is created has 1000 colors (10 saturation levels (or shades) per primary color (blue, green, red)). The number of colors that can be displayed at one time on a color graphics monitor will depend on the graphics monitor being used. For example, if the graphics monitor can only display 512 colors at one time, then the user must run the GRASS command d.colormode mode=fixed before displaying the raster map layer. The colors that cannot be displayed will be assigned to the nearest displayable color, and the raster map layer will retain its relative color accuracy. If the user is in float colormode, however, the raster map layer displayed on the graphics monitor will not accurately reflect the map's real color assignments.

The user is then asked to name the composite image raster map layer. The percentage completed is echoed to the screen and r.support files are created automatically.

NOTES

The user should always check the geographic region settings before running most imagery commands. It is very easy for the boundaries of the geographic region to be completely off the image. Before running i.composite, or other imagery commands, the user should probably set the geographic region to match that of the raster map layers to be read. This can be accomplished using option 4 of the g.region command.

This program is interactive and requires no command line arguments.

SEE ALSO

GRASS Tutorial: Image Processing

d.colormode
d.his
d.rast
g.region
i.colors
i.grey.scale
i.group
r.support

AUTHOR

Michael Shapiro, U.S.Army Construction Engineering Research Laboratory