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Performance evaluation report on shape matching

A performance evaluation on shape matching based on the pre-symmetry diagram has been made. The algorithm has been developed and implemented including a distance measure on shapes. A database of 99 shapes divided in 11 classes. The same shape database is used by Kimia, Sebastian et al. The results are that the total amount of errors compared to the human observer classification is given by (0, 3, 6, 6, 12, 17, 24, 28, 42, 43, 58). Each number in the tupple is in the range 0 to 99. The first position is the sum of the errors among all the best matches to each shape in the database. An error is 0 if the match belongs to the class as query shape and is 1 if the match belongs to another class than the query. The matching algorithm does not in its current form handle severe occlusion. If the three most clear occlusion-caused cases are left out of the match, the above result is improved to (0, 0, 3, 5, 9, 15, 22, 25, 39, 41, 56). This means that the two best suggested matches by the method will always give a shape in the right class, etc. The results are worse than the current state-of-the-art on this database and comparable to early results using the medial axis as shape representation. The current state-of-the-art result from the latest tuned method on the used database is (0, 0, 0, 1, 1, 3, 4, 5, 13).

This result shows that the symmetry sets may be used for characterizing shapes and effective in shape retrieval. This can be the core technology in content-based image database queries.

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