Page 329 - Electrical Engineering Dictionary

graphic adapter an adapter for inter- gravitational torque torque that depends
facing the computer toward a monitor. See upon the position of the robot in the gravita-
MDA, CGA, EGA, VGA. tional field.

graphic controller See graphic adapter. Gray book See IEEE Color Books.

graphical kernel system (GKS) a stan- Gray code a code in which each of a
dard for computer graphics recognized by sequence of code words differs by one bit
both ANSI and ISO. GKS defines the ma- from the preceding one, and the assigned
nipulation of graphic objects, including their value of each code word is one more than
visualization, print, etc. All manipulation is that of the preceding one. Such a code
performed by regarding the graphic adoption avoids glitches (i.e., sharp momentary un-
as a independent device driver. In this way, wanted spikes) when, in an electromechani-
GKS applications can be executed on differ- cal system, the sensors giving the code words
ent kinds of graphics adapters. are imperfectly aligned. For example, one
possible three-bit Gray code is:
graphics the discipline dealing with the
000 001 011 010 110 111 101 100.
generation of artificial images by a computer.
Its two main aspects are geometric modeling,
whose subject is the computational represen- gray level the individual numerical value
tation of the geometry and topology of ob- corresponding to a particular degree of
jects and scenes, and rendering, which stud- brightness in a digital image, often on an 8-
ies the generation of images from the interac-
bit gray scale consisting of 256 gray levels
tion of light and objects. Graphics has been
stretching from pure black to pure white.
generalized to the synthesis of animated im-
age sequences, in which case one speaks of gray level co-occurrence a means of
computer animation. Also called computer measuring texture and other brightness varia-
graphics, image synthesis. tions in digital images by generating matrices
which tabulate the frequencies with which
Graphics Interchange Format (GIF) a different gray levels co-exist at different dis-
popular image-file format that compresses tance vectors from each other.
the image with LZW coding. See also
file format, image compression, Lempel-Ziv- gray level saturation the restriction of
Welch (LZW) coding. image gray scale so that intensities above a
TheGraphicsInterchangeFormat(c)isthe certain level become fixed at the white level
Copyright property of CompuServe Incorpo- corresponding to the highest numerical value
rated. GIF(sm) is a Service Mark property of available within the current storage capacity,
CompuServe Incorporated. typically one byte, of each pixel.

grating See diffraction grating. gray scale (1) an optical pattern in discrete
steps between light and dark.
grating lobe a lobe in an antenna radiation (2) intrinsic modulation property of the
pattern whose peak amplitude is equal to that marking technology that enables dots of ei-
of the main lobe. ther different size or intensity to be printed.
(3) in digital images, a method used to
grating spectrometer an instrument that represent varying levels of brightness. Typi-
provides a spectral decomposition of a opti- cally, gray images use 8-bit gray level for the
cal source using a diffraction grating to give gray scale so that for each picture element, 0
spatial dispersion of wavelengths. represents pure black and 255 represent pure

c
2000 by CRC Press LLC