Fig. 4
From: A variant of the Hough Transform for the combined detection of corners, segments, and polylines
Examples of the different kinds of line segment endpoints considered in the proposed detection method. a Original gray image. b Line segments obtained by an edge detection process. In this second image, corners are marked with green squares and non-intersection endpoints with red circles. Corners correspond to the crossing points of two line segments at a certain range of angles. Non-intersection endpoints appear in the intersections of line segments with the image boundaries as well as in the start and end points of the open polylines resulting from image areas with progressive gray-level variations