Polygon Matching and Indexing Under Affine Transformations

04/18/2013

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by   Edgar Chávez, et al.

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Given a collection {Z_1,Z_2,...,Z_m} of n-sided polygons in the plane and a query polygon W we give algorithms to find all Z_ℓ such that W=f(Z_ℓ) with f an unknown similarity transformation in time independent of the size of the collection. If f is a known affine transformation, we show how to find all Z_ℓ such that W=f(Z_ℓ) in O(n+(m)) time. For a pair W,W^' of polygons we can find all the pairs Z_ℓ,Z_ℓ^' such that W=f(Z_ℓ) and W^'=f(Z_ℓ^') for an unknown affine transformation f in O(m+n) time. For the case of triangles we also give bounds for the problem of matching triangles with variable vertices, which is equivalent to affine matching triangles in noisy conditions.