Browsing by Author "Wei, Dong"

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    Image Data Compression
    (1995-05-01) Wei, Dong; Digital Signal Processing (http://dsp.rice.edu/)
    Wavelet-based multi-resolution representation has become a cutting-edge technology in the area of image data compression. Though the discrete wavelet transform is closely related to the perfect-reconstruction octave-band filter banks used in subband coding schemes, wavelets have provided very promising new ideas and insights for image data compression. Wavelet-based coding techniques have achieved competitive performance compared with other well-known image coding techniques. This thesis develops a general framweork for wavelet-based lossy image coding. We discuss two application problems and develop the corresponding fast algorithms using wavelet-based techniques (e.g., optimum wavelet-packet bases selection, wavelet-domain soft-thresholding).
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    Image data compression using wavelet decomposition
    (1995) Wei, Dong; Burrus, C. Sidney
    Wavelet-based multi-resolution representation has become a cutting-edge technology in the area of image data compression. Though the discrete wavelet transform is closely related to the perfect-reconstruction octave-band filter banks used in subband coding schemes, wavelets have provided very promising new ideas and insights for image data compression. Wavelet-based coding techniques have achieved competitive performance compared with other well-known image coding techniques. This thesis develops a general framework for wavelet-based lossy image coding. We discuss two application problems and develop the corresponding fast algorithms using wavelet-based techniques (e.g., optimum wavelet-packet bases selection, wavelet-domain soft-thresholding).
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    Simultaneous Speckle Reduction and Data Compression using Best Wavelet Packet Bases with Applications to SAR based ATD/R
    (1995-04-20) Wei, Dong; Guo, Haitao; Odegard, Jan E.; Lang, Markus; Burrus, C. Sidney; Digital Signal Processing (http://dsp.rice.edu/)
    We propose a novel method for simultaneous speckle reduction and data compression based on shrinking, quantizing and coding the wavelet packet coefficients of the logarithmically transformed image. A fast algorithm is used to find the best wavelet packet basis in the rate-distortion sense from the entire library of admissible wavelet packet bases. Soft-thresholding in wavelet domain can significantly suppress the speckles of the synthetic aperture radar (SAR) images while maintaining bright reflections for subsequent detection and recognition. Optimal bit allocation, quantization and entropy coding achieve the goal of compression while maintaining the fidelity of the SAR image.