A method is proposed by combining contour-based methods with region-based methods.A closed contour is derived from the object by central projection transformation

and invariant features are extracted from this closed contour.The affine invariance of the closed curve derived by central projection transformation has been proved.An algorithm is provided to extract affine invariant features by employing stationary wavelet transform.Some Chinese characters and 26 capital letters are used to evaluate the proposed method.Experimental results show that the proposed method can efficiently extract invariant features.Compared to traditional methods

the proposed method is robust to noise.