PROCESSING AND DISPLAY 
Image Processing 
As discussed above, input of video data to the computer entails substantial 
preprocessing of pictorial information. A data vector within a resultant video 
file is a list of contemporaneous points; an organism’s outline is represented 
within this data structure as a localized set of points. The user can display such 
data graphically (using the PLOT operator) or alpha-numerically (using the 
LIST or EXAMINE operators). Video files may be edited both in time and in 
space. The EDIT operator allows one to save (or delete) temporally contiguous 
sets of data vectors. Thus, the user could EXAMINE the data to ascertain the 
frame at which the status of a tone had changed (indicating a change in 
stimulus conditions, e.g., switching on a blue light) and then EDIT the data to 
insure that this change occurs on frame number 100. The MASK operator 
allows one to save (or delete) points within rectangular or circular regions of 
the image plane. Thus, the user could MASK out all points within a video file 
which correspond to a particle of detritus within the experimental preparation. 
Finally, the user may APPEND additional information to a video file (text 
describing the conditions of the experiment, numerical constants, time series of 
tone states or time series of experimental variables). 
Analysis of video data by means of the Bugsystem proceeds by abstracting 
one (or more) points from each point set delineating an organism’s outline. In 
an investigation of translational movement this task is easily defined: unlike 
either rotational or flectional movement, quantitative description of the 
translational component of an individual organism’s behavior does not require 
detailed knowledge of the organism’s external anatomy. The body of the 
organism is represented by a single point, viz., its “center of mass”. 
Translational movement is defined as displacement of this point from one 
position in space to another. 
Mapping outlines into centrally located points is usually achieved by means 
of the CENTROID operator whose command syntax is exemplified by the 
entry 
*CENT BUGS.VI BUGS.CE N1, N2, N3. 
Each vector in the resultant file “BUGS.CE” corresponds to a vector in the 
operand file “BUGS.VI”. Each element of a resultant data vector is a 
“centroid”: a point in Bugspace whose X and Y coordinates are, respectively, 
the average X and Y coordinates of an “acceptable set” of points in the 
corresponding operand data vector. The numerical parameters “nl”, “n2” and 
“n3” are required to characterize an “acceptable set” of operand data points. 
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