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Sun, Deqing. / Thesis (M.Phil.)--Chinese University of Hong Kong, 2007. / Includes bibliographical references (leaves 86-91). / Abstracts in English and Chinese. / Abstract --- p.i / 摘要 --- p.iii / Contributions --- p.iv / Acknowledgement --- p.vi / Abbreviations --- p.xviii / Notations --- p.xxi / Chapter 1 --- Introduction --- p.1 / Chapter 1.1 --- Image compression and postprocessing --- p.1 / Chapter 1.2 --- A brief review of postprocessing --- p.3 / Chapter 1.3 --- Objective and methodology of the research --- p.7 / Chapter 1.4 --- Thesis organization --- p.8 / Chapter 1.5 --- A note on publication --- p.9 / Chapter 2 --- Background Study --- p.11 / Chapter 2.1 --- Image models --- p.11 / Chapter 2.1.1 --- Minimum edge difference (MED) criterion for block boundaries --- p.12 / Chapter 2.1.2 --- van Beek's edge model for an edge --- p.15 / Chapter 2.1.3 --- Fields of experts (FoE) for an image --- p.16 / Chapter 2.2 --- Degradation models --- p.20 / Chapter 2.2.1 --- Quantization constraint set (QCS) and uniform noise --- p.21 / Chapter 2.2.2 --- Narrow quantization constraint set (NQCS) --- p.22 / Chapter 2.2.3 --- Gaussian noise --- p.22 / Chapter 2.2.4 --- Edge width enlargement after quantization --- p.25 / Chapter 2.3 --- Use of these models for postprocessing --- p.27 / Chapter 2.3.1 --- MED and edge models --- p.27 / Chapter 2.3.2 --- The FoE prior model --- p.27 / Chapter 3 --- Postprocessing using MED and edge models --- p.28 / Chapter 3.1 --- Blocking artifacts suppression by coefficient restoration --- p.29 / Chapter 3.1.1 --- AC coefficient restoration by MED --- p.29 / Chapter 3.1.2 --- General derivation --- p.31 / Chapter 3.2 --- Detailed algorithm --- p.34 / Chapter 3.2.1 --- Edge identification --- p.36 / Chapter 3.2.2 --- Region classification --- p.36 / Chapter 3.2.3 --- Edge reconstruction --- p.37 / Chapter 3.2.4 --- Image reconstruction --- p.37 / Chapter 3.3 --- Experimental results --- p.38 / Chapter 3.3.1 --- Results of the proposed method --- p.38 / Chapter 3.3.2 --- Comparison with one wavelet-based method --- p.39 / Chapter 3.4 --- On the global minimum of the edge difference . . --- p.41 / Chapter 3.4.1 --- The constrained minimization problem . . --- p.41 / Chapter 3.4.2 --- Experimental examination --- p.42 / Chapter 3.4.3 --- Discussions --- p.43 / Chapter 3.5 --- Conclusions --- p.44 / Chapter 4 --- Postprocessing by the MAP criterion using FoE --- p.49 / Chapter 4.1 --- The proposed method --- p.49 / Chapter 4.1.1 --- The MAP criterion --- p.49 / Chapter 4.1.2 --- The optimization problem --- p.51 / Chapter 4.2 --- Experimental results --- p.52 / Chapter 4.2.1 --- Setting algorithm parameters --- p.53 / Chapter 4.2.2 --- Results --- p.56 / Chapter 4.3 --- Investigation on the quantization noise model . . --- p.58 / Chapter 4.4 --- Conclusions --- p.61 / Chapter 5 --- Conclusion --- p.71 / Chapter 5.1 --- Contributions --- p.71 / Chapter 5.1.1 --- Extension of the DCCR algorithm --- p.71 / Chapter 5.1.2 --- Examination of the MED criterion --- p.72 / Chapter 5.1.3 --- Use of the FoE prior in postprocessing . . --- p.72 / Chapter 5.1.4 --- Investigation on the quantization noise model --- p.73 / Chapter 5.2 --- Future work --- p.73 / Chapter 5.2.1 --- Degradation model --- p.73 / Chapter 5.2.2 --- Efficient implementation of the MAP method --- p.74 / Chapter 5.2.3 --- Postprocessing of compressed video --- p.75 / Chapter A --- Detailed derivation of coefficient restoration --- p.76 / Chapter B --- Implementation details of the FoE prior --- p.81 / Chapter B.1 --- The FoE prior model --- p.81 / Chapter B.2 --- Energy function and its gradient --- p.83 / Chapter B.3 --- Conjugate gradient descent method --- p.84 / Bibliography --- p.86

Many existing researches on image watermarking for copyright protection need to use original image in retrieving watermark. Though it is more robust, it would cause some problems about the authorization of original image. In this thesis, we propose a method based on DCT domain without using original image. Using the property of concentrating energy in DCT transform, the energies of blocks are used for further processing. In the embedding algorithm, the DC coefficients of blocks are first collected. Then they are divided by some number to get remainders. The values of embedded data are embedded in the relationship between corresponding location of embedded data and other locations by adjusting the remainders in all locations. Some typical watermarking attacks and noise are used to evaluate the robustness of our method. Compared with other competing algorithms, it shows that the survival rate of watermark in our method can be almost the same or even better then those methods which need original image. The error rate of the lowest quality JPEG compression can be adjusted less then 1%, when the length of embedding data is 512 bits. Our proposed method can be further improved by adjusting the values of remainders and the block size. These provide flexibility to satisfy different requirements.

Yes / Wavelets are alternative building kernels of the multicarrier systems, such as the orthogonal frequency division multiplexing (OFDM). The wavelets can be designed by changing the parent basis functions or constructing new filters. Some two new wavelets are considered for multicarrier design; one is designed using raised-cosine functions while the other was constructed using ideal filters. The spectrums of raised cosine wavelet filters are controlled by a roll-off factor which leads to many distorting sidelobes. The second family of wavelet, which the raised-cosine wavelet is compared to, have no distorting sidelobes. It will be shown that raised-cosine wavelets are less suitable for multicarrier design in multicarrier environment, in terms of BER when compared to the wavelet constructed from the ideal filter.

Image completion is the process of filling missing regions of an image based on the known sections of the image. This technique is useful for repairing damaged images or removing unwanted objects from images. Research on this technique is plentiful. This thesis compares three different approaches to image completion. In addition, a new method is proposed which combines features from two of these algorithms to improve efficiency.

In our research, we propose two improve methods for detection of dominant points for a digitized curve. Instead of setting a fixed length of support region, it will compute the suitable length of support region for each point to find the best approximated curvature. First, the symmetric region of support for each point on curve is determined using diagonal value. The points with local maximum averaging diagonal value can be located as the dominant points on the curve. Second, the improve method uses an optimal criterion for determining the asymmetric region of support of each boundary point, and a new mechanism for selecting the dominant points.

This paper presents two new schemes for interpolating missing samples in satellite diurnal temperature cycles (DTCs). The first scheme, referred to here as the cosine model, is an improvement of the model proposed in [2] and combines a cosine and exponential function for modelling the DTC. The second scheme uses the notion of a Reproducing Kernel Hilbert Space (RKHS) interpolator [1] for interpolating the missing samples. The application of RKHS interpolators to the DTC interpolation problem is novel. Results obtained by means of computer experiments are presented.

The report detailing the Hardware Accelerator for the JPEG encoder is organized into three sections. First, it will review the processes of the Joint Photographic Experts Group (JPEG) encoding and decoding standard. Second, it will review three different implementations of the discrete cosine transform in hardware. This is a very computationally intensive element of the JPEG encoding process and the analysis of these designs covers the benefits and costs of the various approaches for the Field Programmable Gate Array (FPGA) and Application Specific Integrated Circuit (ASIC) implementations. Finally, it will discuss this specific hardware accelerator design for a color state transformation for the standard JPEG encoder. An eight by eight matrix of Red, Green, Blue (RGB) values is passed into the FPGA as well as calculated in software. The Y Cr Cb results from that of the hardware accelerator implementation are compared with the software implementation for computational accuracy and the differences in computation time are sampled for a comparison. There is a clear 38% improvement in speed from the hardware accelerator. / text

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