Next: tolookup, Previous: tense_loop, Up: Internal Routines [Contents][Index]
threecolors [, argument]
[x11] Installs or uninstalls the "three-colors" color table,
which has three sections. If the argument is a scalar,
then the color table’s sections are grey, red, and blue, respectively,
and the value of argument indicates the contrast level of
the red and blue sections. A value of 1 corresponds to full
contrast, and values close to 0 correspond to hardly any
contrast. A value of 0 uninstalls the "three-colors" color table
in favor of a standard greyscale table.
If the argument is a numerical array, then it must have
nine elements, which govern the bottom, middle, and top sections of the
color table in groups of three numbers. The first of each three numbers
specifies the amount of red in the color table section, the second one
the amount of green, and the third one the amount of blue. The amounts
must be between -1 and +1. Positive numbers indicate that
the intensity level runs from 0 to the indicated fraction, and negative
numbers indicate that the intensity level runs from one minus the
indicated fraction to one. Scalar argument equal to
f is equivalent to an array argument equal to
[1.0, 1.0, 1.0, -f, 0.0, 0.0, 0.0, 0.0, -f].
The "three-color" color table is used by the tv3 and zoom
routines. If tv is used with the three-color color table, then
only colors from the lowest section of the color table are displayed.