Qiong-Hua Wang

Adaptive disparity and motion estimation for Multiview Video Coding

In the joint mode of MVC (Multiview Video Coding), to fully exploit both temporal and inter-view correlation, motion estimation (ME) and disparity estimation (DE) have been employed to achieve the highest coding efficiency. However, it causes enormous computational complexity. An adaptive ME and DE algorithm is proposed to reduce the complexity in this paper. Fist, we calculate the difference between the coding macroblock (MB) and the corresponding MB in the reference frame to determine the region homogeneity. Then, based on the region homogeneity, some INTER modes will be skipped in coding mode selection. Finally, an optimization method of obtaining the optimal motion information from the neighboring view is proposed to speed up rate distortion optimization (RDO) process for Motion Skip (MS) mode. In addition, the search range (SR) for ME and DE can be limited to an estimable range and the disparity search is selectively enabled adaptively. Experimental results demonstrate that the proposed algorithm can save about 78% computational complexity on average, with negligible loss of encoding efficiency.

Single-channel optical encryption of color image using chessboard grating and diffraction imaging scheme

Abstract. A single-channel encryption method for color images is proposed using chessboard grating and a phase-retrieval algorithm in the Fresnel domain. The pixel sampling operation is introduced to convert the color image to be encrypted into a Bayer image. Thereafter, with a single channel, the Bayer image is encoded by the chessboard grating before being sent into a diffractive-imaging-based encryption scheme. The cryptosystem is simple owing to only one single intensity pattern being required during encryption. In the decryption procedure, the phase-retrieval algorithm and the chessboard grating are combined to extract the plaintext from the intensity pattern. This proposal not only can successfully encrypt a color image into a single diffractive intensity pattern but also can recover the primary color image with high quality from the one single diffraction pattern with a compact optical setup. Numerical simulations are carried out to prove the feasibility and validity of the proposal.

Optical encryption of gray image based on the fourier computer generated hologram and logical modulation

In this paper, we proposed a novel optical encryption and decryption method of gray image based on the Fourier computer-generated hologram (CGH) and logical modulation. Since the encryption method using the CGH or the logical modulation alone has a shortness of low security, the proposed novel encryption combines the two methods together. In our encryption processing, the hologram, which is gotten by Fourier transform from the original image, is encrypted by logical modulation with the chaotic sequence. Simulation results and analysis show that the security and robustness of the proposed approach has a satisfactory performance.

A novel encryption method of color image combining Hadamard transform with logical modulation

In this paper, a novel encryption and decryption method for color images based on the Hadamard transform (HT) and logical modulation has been proposed. Firstly, considering security and efficiency, together, our cryptosystem combined with image compression can reduce encryption time and promote real-time secure image transmission and storage. Then the compressed image is encrypted by logical modulation with chaotic sequence in HT domain. Furthermore, the validity and feasibility of proposed method is demonstrated by experimental simulation results in the case of ensuring good quality of recovered image.