Contour Retrieval and Matching by Affine Invariant Fourier Descriptors

In the image plane, a 3 Dimensional movement of planar rigid object can be represented satisfactory by an affine motion of his boundary (the exterior contour) which we assume to be closed. The object movement can be described by a special affine transformation of the plane IR 2 . The extraction of invariant features under affinities is important in such procedure. Recently we have proposed a new shape representation invariant to affine transformation based on Fourier descriptors [3]. The performances of the new family was analysed with experiments on the numerical invariance, the robustness of the shape features and the invariance to parameterization [3][4]. In this paper, we present two applications of the affine descriptors for contour-based retrieval and curve matching. Experimental results on a curve database subject to perspective distortions show that these features are very robust against such distortions. A comparative study with other affine invariant descriptors will be presented in the context of contour retrieval.