GAMMA(6T) GAMMA(6T)
NAME
gamma - demonstrates gamma correction using the color map.
SYNOPSIS
/usr/people/tutorial/c.graphics/online/gamma
DESCRIPTION
gamma shows the effects of gamma correcting a color ramp us-
ing the IRIS Graphics Library mapcolor routine. Use the
left mouse button to control the slider bars that change the
value of the gamma constant.
Display Windows
gamma has three windows. The information window contains
instructions for using the mouse buttons. The control win-
dow contains the control bar for editing gamma values. The
graph window contains a curve that shows the intensity ramp
generated by the given gamma. There are also two color
ramps. One is gamma corrected, and the other is linear.
Pop-up Menu Operation
Press the right mouse button to display a pop-up menu. To
select an item from the menu, move the cursor until the item
is highlighted, and then release the button. To eliminate
the menu without selecting an item, move the cursor out of
the menu and release the button.
When you select the first item, "reset gamma to 1.0", the
IRIS resets the gamma value to 1.0. This produces a linear
color ramp. When you select the last item, "exit program",
a second pop-up menu appears which asks you to confirm this
selection. Select "yes" from this menu to terminate the
program; select "no" to return control of the program to
the original pop-up menu.
Slider Bar Operation
To change a slider bar value, move the cursor over the bar,
press and hold the left mouse button, and move the cursor
back an forth to change the value. In this program, the
slider bar changes the gamma value. The top color ramp
changes to reflect the new value of gamma. If you move the
cursor off the ends of the slider bar, the cursor automati-
cally jumps to the other end of the bar, the values at the
ends of the bar change to mark the new range, and you can
continue moving the cursor in the desired direction.
Window Manager
This program runs only in the window manager. It uses the
first 48 colors in the color map so any other programs using
those colors affect the display on this program or may be
affected by this program when running in the window manager.
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GAMMA(6T) GAMMA(6T)
HARDWARE REQUIREMENTS
Your IRIS needs 16 bitplanes to run this program.
BUGS
Since the parameters are 32-bit floating point numbers, you
can obtain a maximum and minimum value. If you exceed these
values, the program has undefined results. Also, using the
left mouse button to alter values and simultaneously using
the right mouse button to work the pop-up menu causes
unpredictable results.
AUTHOR
Mason Woo
ORIGIN
Silicon Graphics, Inc.
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