The Orientation Angle Detection of Multiple Insulators in Aerial Image - Advances in Image and Graphics Technologies - page 298

approximate the irregular curve contour shown in Fig. 4(b). Thus each contour is
composed by plenty straight line segments and the points in each contour can be
formed as a list of connected edge points.
(a) (b)
Fig. 4. Curve edge of Im 1 and processed edge. (a) Curve edge of Im 1. (b) Processed edge.
Define the orientation angle for each point in each list, and all the angles are com-
posed of a set of sequential angular variation. The points with sign-Changing angle
would be extracted as candidate points. If the number of candidate points of the con-
tour is too less, the contour can be ignored as pseudo-insulator.
Shown in Fig. 5, a , b , c is three adjacent edge points in the list of the contour. De-
fine the angle of vertical direction is 0°, then the angle of a is -45°and the angle of b
and c is 45°, thus b is the points with sign-Changing angle which can be defined as
candidate point. And Fig. 6 shows candidate points of each connected contour in Im 1.
Fig. 5. The schematic of orientation angles of edge points
Fig. 6. Candidate points of Im 1