A new criterion for multilevel thresholding is proposed. The criterion is based on the consideration of two factors. The first one is the discrepancy between the thresholded and original images and the second one is the number of bits required to represent the thresholded image. Based on a new maximum correlation criterion for bilevel thresholding, the discrepancy is defined and then a cost function that takes both factors into account is proposed for multilevel thresholding. By minimizing the cost function, the classification number that the gray-levels should be classified and the threshold values can be determined automatically. In addition, the cost function is proven to possess a unique minimum under very mild conditions. Computational analyses indicate that the number of required mathematical operations in the implementation of our algorithm is much less than that of maximum entropy criterion. Finally, simulation results are included to demonstrate their effectiveness.

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We propose a new signal security system and its VLSI architecture for real-time multimedia data transmission applications. We first define two bit-circulation functions for one-dimensional binary array transformation. Then, we exploit a chaotic system in generating a binary sequence to control the bit-circulation functions defined for performing the successive transformation on the input data. Each eight 8-bit data elements is regarded as a set and is fed into an 8×8 binary matrix being transformed on each row and each column of the matrix by these two bit-circulation functions such that the signal can be transformed into completely disordered data. The features of the proposed design include low computational complexity, regular operations suitable for low-cost VLSI implementation, high data security, and high feasibility for easy integration with commercial multimedia storage and transmission applications. We have performed Matlab simulation to verify the functional correctness of the proposed system. In implementing the system, a low-cost VLSI architecture has been designed, verified, and physically realized based on a 0.35 μm CMOS technology. The implementation results show that the proposed signal security system can achieve 117 Mbytes/s data throughput rate that is fast enough for real-time data protection in multimedia transmission applications

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