NAME

d.his - Produces and displays a raster map layer combining hue, intensity, and saturation (his) values from user-specified input raster map layers.
(GRASS Display Program)

SYNOPSIS

d.his
d.his help
d.his h_map=name [i_map=name] [s_map=name] [out=name]

DESCRIPTION

his stands for hue, intensity, and saturation. This program produces a raster map layer 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 one new raster map layer which retains the original information in terms of hue, intensity, and saturation.

OPTIONS

This program can be run non-interactively or interactively. It will run non-interactively if the user specifies on the command line the name of a map containing hue values (h_map), and the name(s) of map(s) containing intensity values (i_map) and/or saturation values (s_map). If the user also names an output map (out) on the command line, the combined hue, saturation, and intensity values will be saved as a raster map layer in the user's current mapset; otherwise, the resulting image will only be displayed in the active display frame on the graphics monitor.

Alternately, the user can run the program interactively by typing d.his without naming parameter values on the command line. In this case, the program will prompt the user for parameter values using the standard GRASS parser interface.

Parameters:

h_map=name
Name of input raster map layer to be used for HUE values.
i_map=name
Name of input raster map layer to be used for INTENSITY values.
s_map=name
Name of input raster map layer to be used for SATURATION values.
out=name
Name of the output raster map layer combining hue, intensity, and saturation values from input layers.

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 raster map layer 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.display or d.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

This program produces an image and (optionally) a raster map layer with 1000 colors (10 intensities each of red, green, and blue). The resulting image and raster map layers will not display properly if the graphics display monitor 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 command:
d.colormode mode=fixed
before running d.his. Otherwise, the colors will be incorrectly displayed on the graphics monitor.

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.

SEE ALSO

d.3d
d.colormode
d.colors
d.colortable
d.display
hsv.rgb.sh
rgb.hsv.sh
parser

AUTHOR

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