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2.2.D. Additional techniques.

To avoid a repeated finding of segments and to simplify searching less expressed maximums,
the contour points laying inside the image piece corresponding the found segment, were excluded from the further reviewing. Each of such pieces represents a corridor in width 2D/0.7, enclosing the axial line of the given segment; length of branches of this corridor - B1/0.7 and B2/0.7 (fig.9).


To avoid superfluous losses of time, the operation of rough choice of the contour points concerning to the flowing contiguous segment was applied. In the beginning for an evaluation of coincidence measure gradient of chosen contour points (the list of references to their initial set is formed) which lay inside a wide rectangle enclosing the contiguous segment in its flowing position (such neighbourhood is shown by fat primes on fig.12).


Further, on each step a possibility of build-up of new, narrower neighbourhood for a flowing position of the contiguous segment (thin primes on fig.12), not passing out of former wide neighbourhood is checked. If it is impossible, a list of references is made on a new wide neighbourhood.

Operations of deletion and preliminary choice have not only engineering sense. A solution of basic problems depends on their organization too. In particular, ability of the procedure to understand complicated situations depends on their organization, - at processing of false concentrations of contour points, in the case of capture of several segments. In similar cases the number of steps noticeably increased (sometimes so, that it was necessary to discontinue compulsorily process of searching). Detection of such situations was carried out by criterion of filling ratio of resulting segments by contour points. An example of such situation is shown on fig.11. On this picture it is shown the initial (dotted line) and finite (solid line) positions of the contiguous segment, corresponding to process of search of one local maximum. Apparently, the right branch of the initial contiguous segment has not had time to be rounded along the corresponding piece of the contour line and intersected an adjacent contour.


Thus it is obvious, that deletion of the piece of image corresponding to the finite position of such segment is wrongful. The contiguous segments started from other initial positions can correctly interpret an observed picture. The solution accepted in this occasion is based on this reason. The elementary contours laying in a neighbourhood of the contour movement from which led to an unacceptable segment, were excluded from candidates in initial approximations. So the situation shown on fig.11, for example, was treated - as an initial approximation the elementary segment was chosen, the distance from which up to an outside contour exceeded the corresponding distance for the initial segment which had led to false outcome.

This example illustrates common logic of solution of complicated situations. To solve them it is necessary to begin from the outside - from the "free" ends of entering lines.