1. A method of determining symmetry in an image, the method including: a) determining at least one searching line segment within a predefined search area of an image portion, the at least one searching line segment including a reference point (x, y) at its center and an angle &thgr; with respect to a predetermined axis of the image portion; b) for each searching line segment, determining a first local characteristic in accordance with a measurement at points adjacent the searching line segment; and c) determining the symmetry in the image in accordance with a calculation based on the first local characteristic.