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Issue No.06 - June (2010 vol.32)
pp: 961-973
Tetsuo Shima , Tokyo Institute of Technology, Tokyo
Suguru Saito , Tokyo Institute of Technology, Tokyo
Masayuki Nakajima , Tokyo Institute of Technology, Tokyo
Digital two-dimensional images are usually sampled on square lattices, while the receptors of the human eye are following a hexagonal structure. It is the main motivation for adopting hexagonal lattices. The fundamental operation in many image processing algorithms is to extract the gradient information. As such, various gradient operators have been proposed for square lattices and have been thoroughly optimized. Accurate gradient operators for hexagonal lattices have, however, not been researched well enough, while the distance between neighbor pixels is constant. We therefore derive consistent gradient operators on hexagonal lattices and compare them with the existing optimized filters on square lattices. The results show that the derived filters on hexagonal lattices achieve a better signal-to-noise ratio than those on square lattices. Results on artificial images also show that the derived filters on hexagonal lattices outperform the square ones with respect to accuracy of gradient intensity and orientation detection.
Image processing, hexagonal lattice, consistent gradient operator, gradient intensity, orientation.
Tetsuo Shima, Suguru Saito, Masayuki Nakajima, "Design and Evaluation of More Accurate Gradient Operators on Hexagonal Lattices", IEEE Transactions on Pattern Analysis & Machine Intelligence, vol.32, no. 6, pp. 961-973, June 2010, doi:10.1109/TPAMI.2009.99
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