The gamma command accepts a single floating-point argument. A value of 1.0
creates a strictly linear color ramp. Values above 1.0 increase the brightness in
the middle of a color ramp; values below 1.0 decrease the brightness. Values
between 1.0 and 3.0 are typical.
The gamma program does not immediately affect the color map. It stores its
argument in a file called .gamma in your home directory. Whenever a color
ramp is made, such as in the program demomakemap, this file is referenced for a
value for gamma. The gamma program itself does not open a window.
Below is an exercise in running the previously described programs. To run
these programs, use the following procedure:
1. Bring up the windows showmap and showramp.
2. Set the gamma correction value and use it to change the color map:
gamma 0.5
demomakemap
Wait a moment for the colors to change. Observe the effects on the
object and the brightness and smoothness of the color ramps in the
showmap and showramp windows. (demomakemap does not open a
window.)
3. Repeat the experiment with a different gamma value:
gamma 3.0
demomakemap
Remember that the value you select for gamma is saved until you
change it.
cedit is an interactive color editor in a graphics window. To use cedit:
1. Bring up the cedit window and select it for input.
2. To select a color index for editing, move the cursor to a pixel outside
the cedit window itself.
3. To choose the color index of the pixel, press the LEFTMOUSE
button and release it.
The selected color index is painted on the “sample chip” on the
right of the cedit window, and the “color sliders” are set to the red,
green, and blue values of that color.
4. To change the intensity of the color value of the sample chip, press
the LEFTMOUSE button down while the cursor is located on one of
the three color sliders and move the sliders up and down.
9-4 IRIS OWNER’S GUIDE
SERIES 3000 Version 1.1
Demonstration Programs and Gifts
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