Abstract
A SIFT (Scale Invariant Feature Transform) feature based registration algorithm is presented to prepare for the seal
verification, especially for the verification of high quality counterfeit sample seal. The similarities and the spatial
relationships between the matched SIFT features are combined for the registration. SIFT features extracted from the
binary model seal and sample seal images are matched according to their similarities. The matching rate is used to define
the similar sample seal that is similar with its model seal. For the similar sample seal, the false matches are eliminated
according to the position relationship. Then the homography between model seal and sample seal is constructed and
named HS . The theoretical homography is namedH . The accuracy of registration is evaluated by the Frobenius norm of
H-HS . In experiments, translation, filling and rotation transformations are applied to seals with different shapes, stroke
number and structures. After registering the transformed seals and their model seals, the maximum value of the
Frobenius norm of their H-HS is not more than 0.03. The results prove that this algorithm can accomplish accurate
registration, which is invariant to translation, filling, and rotation transformation, and there is no limit to the seal shapes,
stroke number and structures.
