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Author: search.filters.author.Hamamoto, KazuhikoSubject: search.filters.subject.Discrete wavelet transform

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    Medical image compression using vector quantization and system error compression
    (2015-09-01)
    Phanprasit, Tanasak
    ;
    Hamamoto, Kazuhiko
    ;
    Sangworasil, Manas
    ;
    Pintavirooj, Chuchart
    A novel medical image compression scheme based on vector quantization (VQ) is proposed in this paper. The advantages of the technique are not only that it yields high compression ratio but also that it maintains a peak signal-to-noise ratio (PSNR). This new method involves three steps. First, we present a codebook design using discrete wavelet transform (DWT), fuzzy C-means (FCM), and support vector machine (SVM) algorithms. Second, we improve the bit rate using the Huffman coding theme as a method of eliminating the redundant index. Finally, we supplement the system with error compensation to improve the PSNR. With the proposed method, we are able to achieve a bit rate improvement of 24.00% and a PSNR of 10.96% over the conventional method.
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    A new correlation-based watermarking method using wavelet tree and mathematical morphology
    (2009-01-01)
    Sepsirisuk, Kasemsuk
    ;
    Hamamoto, Kazuhiko
    ;
    Atsuta, Kiyoaki
    ;
    Kondo, Shozo
    This paper proposes a new correlation-based watermarking method using the wavelet tree and the mathematical morphology. In this method a watermark is a two-dimensional pseudorandom array of {-1, 1} with the same size as a host image to be watermarked. The watermark is embedded into a Resilient Tree Structure (RTS) which is created by applying the mathematical morphology, the dilation operation, to the wavelet tree. The dilation operation improves the reliability of the proposed method by increasing the number of coefficients involved in watermarking. Furthermore an improved perceptual weighting function of the Human Visual System is used for preserving the image quality. In a watermark detection process the linear correlation between the watermark and the coefficients of the RTS of a tested image is computed to judge the presence of the watermark. The experimental results show that the proposed method outperforms current correlation-based watermarking methods. © 2009 The Institute of Electrical Engineers of Japan.