Proceedings 2nd International Symposium on 3d Data Processing Visualization and Transmission 2004 3dpvt 2004, Sep 5, 2004
This paper presents a stereoscopic image coder based on the MRF model and MAP estimation of the d... more This paper presents a stereoscopic image coder based on the MRF model and MAP estimation of the disparity field. The MRF model minimizes the noise of the disparity compensation because it takes into account the residual energy, smoothness constraints and the occlusion field. The disparity compensation is formulated as a MAP-MRF problem in the spatial domain and the MRF field consists of the disparity vector and occlusion field, which is partitioned into three regions by an initial double-threshold setting. The MAP search is conducted in a block-based sense on one or two of the three regions, providing faster execution. The reference and the residual images are decomposed by a discrete wavelet transform and the transform coefficients are encoded by employing the morphological representation of wavelet coefficients algorithm. As a result of the morphological encoding, the reference and residual images together with the disparity vector field are transmitted in partitions lowering the total entropy. The experimental evaluation on synthetic and real images shows beneficial performance of the proposed algorithm.
In this paper, a robust watermarking algorithm using the wavelet transform and edge detection is ... more In this paper, a robust watermarking algorithm using the wavelet transform and edge detection is presented. The efficiency of an image watermarking technique depends on the preservation of visually significant information. This is attained by embedding the watermark transparently with the maximum possible strength. The watermark embedding process is carried over the subband coefficients that lie on edges, where distortions are less noticeable, with a subband level dependent strength. Also, the watermark is embedded to selected coefficients around edges, using a different scale factor for watermark strength, that are captured by a morphological dilation operation. The experimental evaluation of the proposed method shows very good results in terms of robustness and transparency to various attacks such as median filtering, Gaussian noise, JPEG compression and geometrical transformations.
This paper describes the implementation of a system-on-a-programmable-chip (SOPC) development boa... more This paper describes the implementation of a system-on-a-programmable-chip (SOPC) development board to support computer architecture laboratories at a low cost. A commercial field-programmable gate-array (FPGA) was employed to develop our reducedinstruction-set-computer (RISC) soft processor core that may be programmed through a userfriendly environment consisting of an assembler and a remote operation interface. Our approach aims to support a wide variety of student projects in our engineering curriculum, increase students productivity and decrease the development time. Through the proposed implementation, students are introduced to RISC architecture concepts, SOPC design and assembler structure. The reusability of the hardware permits flexible materialization of future projects to suit a variety of educational needs. The proposed inexpensive solution forms a complete educational environment suitable for undergraduate use.
The efficiency of an image watermarking technique depends on the preservation of visually signifi... more The efficiency of an image watermarking technique depends on the preservation of visually significant information. This is attained by embedding the watermark transparently with the maximum possible strength. The current paper presents an approach for still image digital watermarking in which the watermark embedding process employs the wavelet transform and incorporates Human Visual System (HVS) characteristics. The sensitivity of a human observer to contrast with respect to spatial frequency is described by the Contrast Sensitivity Function (CSF). The strength of the watermark within the decomposition subbands, which occupy an interval on the spatial frequencies, is adjusted according to this sensitivity. Moreover, the watermark embedding process is carried over the subband coefficients that lie on edges where distortions are less noticeable. The experimental evaluation of the proposed method shows very good results in terms of robustness and transparency.
In this paper, we propose an adaptive method of image de-noising in the wavelet subband domain. T... more In this paper, we propose an adaptive method of image de-noising in the wavelet subband domain. This approach is based on threshold estimation for each subband of the wavelet decomposition of a noise-contaminated image, by considering that the subband coefficients have a Generalized Gaussian Distribution (GGD). Under this framework, the proposed technique estimates the threshold level by applying a robust
In this paper, a new optimised method of coding stereoscopic image sequences is presented and com... more In this paper, a new optimised method of coding stereoscopic image sequences is presented and compared with already known methods. Two basic methods of coding a stereoscopic image sequence are the compatible and joint. The first one uses MPEC for coding the left channel and takes advantage of the spatial disparity redundancy between the two sequences for coding the right channel. The second one employs MPEG for coding the left channel but takes advantage of both temporal redundancy among the right channel frames and spatial redundancy between the corresponding frames of the two channels The proposed method, which is called IMDE, estimates the P and B type of frames of the right channel by an interpolative scheme that takes in to account both the temporal and disparity characteristics. Investigating the effectiveness of the joint motion and disparity vectors estimation as well as the choice of the weighting factors that participate in the proposed interpolative scheme optimises the w...
In this paper, we propose a new stereo image compression scheme that is based on the wavelet tran... more In this paper, we propose a new stereo image compression scheme that is based on the wavelet transform of both images and the disparity estimation between the stereo pair subbands. The two images are decomposed by using a Discrete Wavelet Transform (DWT) and coded by employing the morphological representation of the wavelet coefficients, which is a technique that exploits the intraband-interband statistical properties of them. The progressive pixel-to-pixel evaluation of the disparity has been incorporated to the morphological coder so that a dense disparity field to be formed for every subband. The proposed method demonstrates very good performance as far as PSNR measures and visual quality are concerned and low complexity.
AbstractThe efficiency of an image watermarking technique depends on the preservation of visuall... more AbstractThe efficiency of an image watermarking technique depends on the preservation of visually significant information. This is attained by embedding the watermark transparently with the maximum possible strength. The current paper presents an approach for still ...
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