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15.5.637 threecolors

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.

See also: tv3, tvlct, zoom