An Efficient Primitive-Based Method to Recognize Online Sketched Symbols with Autocompletion

Table 1

List of features for corner finding.

Feature	Description	Reference
Cost	The cost of removing the vertex, from (1).	[29]
Diagonal	The diagonal length of the stroke’s bounding box.
Ink density	The length of the stroke divided by the diagonal length.
Max distance	The distance to the farther of its two neighbors ( or ) normalized by the distance between the two neighbors.
Min distance	The distance to the nearer of its two neighbors normalized by the distance between the two.
Sum distance	The sum of the distances to the two neighbors normalized by the distance between the two.
EllipseFit	A function calculated on the whole stroke, returning a real value between 0 and 1. The higher this value is, the more the stroke resembles an ellipse (or a circle).	[7]
PolyFit	A function calculated for the candidate corner point on the substroke whose endpoints are the previous and the next candidate corner ( and , resp.), returning a real value between 0 and 1. The higher this value is, the more the stroke resembles a polyline composed of the two segments and .
Angle	The magnitude of the angle with vertex in the candidate corner point, calculated with respect to the previous and the next sampled points of the stroke.
SeqNumber	The sequence number of the iteration of the removal process.