d.rgb

NAME

d.rgb - Displays three user-specified raster map layers as red, green, and blue overlays in the active graphics frame.
(GRASS Display Program)

SYNOPSIS

d.rgb
d.rgb help
d.rgb [red=name] [green=name] [blue=name] [out=name]

DESCRIPTION

RGB stands for red, green, and blue. This program visually overlays up to three raster map layers, each displayed in either red, green, or blue. As each overlay is displayed in a single band, the intensity at each point is the average intensity of the red, green, and blue components of the currently active color table. For example, any cell that carries 100% intensity for either red, green, or blue and 0% intensity for the other two colors will be represented at 33% intensity.

WARNING: Maps that are using the "color wave" color table appear to be solid grey when using d.rgb. The average intensity of the colors being used is always 33%.

This program sacrifices spatial resolution to provide full color information. Any color that cannot be fully represented at a particular pixel passes the extra color to the next cell right and down. For example, if a cell is to show 50% red, but the closest color available (without showing more than 50%) is 40%, the pixle to the right and the pixle below will be given an extra 5% red each. In this way all the color is provided at the small cost of a slight amount of blurring. The result is very pleasing, especially on high resolution screens.

OPTIONS

Parameters:

red=name: Name of raster map layer to be used for RED component.
green=name: Name of raster map layer to be used for GREEN component.
blue=name: Name of raster map layer to be used for BLUE component.
out=name: Name of raster map layer to contain results.

NOTES

It produces an image and (optionally) a raster map layer with 1000 colors (10 intensities each of red, green and blue). The image and raster map layers will not display properly if the graphics device does not have at least 1000 colors while the user is running in float colormode. Thus, unless the display device has 1000 colors, it is necessary to run the GRASS program

d.colormode mode=fixed

before running d.rgb. Otherwise, the colors will be incorrect.

AUTHOR

James Westervelt, U.S. Army Construction Engineering Research Laboratory