Artificial Intelligence and Soft Computing: Behavioral ... - Arteimi.info

G
H
Fig. 17.7: A region boundary to illustrate the construction
of the chain code.
Suppose we arbitrarily start coding from point A along AB. Suppose
we have a small fixed length stick, by which we measure line AB and write
the code for horizontal right (0) (vide fig. 17.6) as many times as the number
of the measuring stick. Last time the stick length may have been a little
larger/smaller than the actual length of the remnant line. Let us assume that
AB is 4 times the length of our measuring stick; so we write 4 zeroes to
describe AB. Proceeding in this manner, we find the chain code of the closed
boundary as follows.
Chain code= { 00003311333445557755}
Rewriting repeated consecutive symbols once only, we find the
modified code = {03134575}. Since it is a closed chain, we can start
anywhere. But the code must start with the minimum index. Here, it is
already in the required form. For a specific example let the chain code be
{2304568}; we would express it in the form {0456823}, which starts with the
minimum index. Such representation helps matching the code of an unknown
boundary with known ones. It may be noted that for two distinct shapes of
boundaries the chain code must be different. If it is not the case, then direction
indices need to be increased.
17.4 High Level Vision
F
A B
The major task of high level vision is to recognize objects from their feature
space, obtained at earlier levels, and interpret the scene comprising of one or
more objects. For instance, suppose a football tournament is going on and the
E
C
D