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A Fast VQ Codebook Generation Algorithm Based on Otsu Histogram Threshold

Huang C-C., Tsai D-S., Horng G.

Fundamenta Informaticae

2009

Vol. 91, nr 3-4

563-579

In vector quantization, the codebook generation problem can be formulated as a classification problem of dividing N_p training vectors into N_c clusters, where N_p is the training size of input vectors and N_c is the codeword size of codebook. For large Np and Nc, a traditional search algorithmsuch as the LBG method can hardly find the global optimal classification and needs a great deal of calculation. In this paper, a novel VQ codebook generation method based on Otsu histogram threshold is proposed. The computational complexity of squared Euclidean distance can be reduced to O(N_p log_2 N_c) for a codebook with gray levels. Our method provides better image quality than recent proposed schemes in high compression ratio. The experimental results and the comparisons show that this method can not only reduce the computational complexity of squared Euclidean distance but also find better codewords to improve the quality of the resulted VQ codebook.

Histogram Thresholding using Beam Theory and Ambiguity Measures

Sen D., Pal S.K.

Fundamenta Informaticae

2007

Vol. 75, nr 1-4

483-504

This paper presents a novel histogram thresholding technique based on the beam theory of solid mechanics and the minimization of ambiguity in information. First, a beam theory based histogram modification process is carried out. This beam theory based process considers a distance measure in order to modify the shape of the histogram. The ambiguity in the overall information given by the modified histogram is then minimized to obtain the threshold value. The ambiguity minimization is carried out using the theories of fuzzy and rough sets, where a new definition of rough entropy is presented. The applications of the proposed scheme in performing object and edge extraction in images are reported and compared with those of a few existing classical and ambiguity minimization based schemes for thresholding. Experimental results are given to demonstrate the effectiveness of the proposed method in terms of both qualitative and quantitative measures.