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 hght) 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 wdthin 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 Nl , 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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