Abstract: We extend Chen's methods to define structure moments, which are independent of position, scale and orientation. The formula of invariant moments we proposed can be applied to closed and unclosed structures. In a discrete image plane, chain codes are often used to represent structures, However the moment calculation based on chain codes is complex. We propose a fast algorithm to compute the structure moments. This algorithm also reduce calculation errors. Experiments shows that this fast algorithm performs well.

Key words: image recognition, geometric shapes recognition, structure moment invariants, fast algorithm