Table 1.

Features of an event region.

Feature	Definition
Amp	Amplitude of time-space domain signal
Cen	Minimum interval between regions
Shape	Roundness of the region
Con	Pixel number of the convex hull
Area	Pixel number of the region
Ecc	Eccentricity of ellipse which has the same second moment as the event region
Maj	Length of the long axis of the ellipse which has the same second moment as the event region
Min	Length of the short axis of the ellipse which has the same second moment as the event region
Equ	Diameter of a circle which has the same total area as the event region
Eul	Remaining number of objects, excluding holes in the image region