In this paper we proposed a novel method of viewpoint selection using the hybrid Nelder-Mead (NM) simplex search and particle swarm optimization (PSO) to improve the efficiency and the intelligent level of volume rendering. This method constructed the viewpoint quality evaluation function in the form of entropy by utilizing the luminance and structure features of the two-dimensional projective image of volume data. During the process of volume rendering, the hybrid NM-PSO algorithm intended to locate the globally optimal viewpoint or a set of the optimized viewpoints automatically and intelligently. Experimental results have shown that this method avoids redundant interactions and evidently improves the efficiency of volume rendering. The optimized viewpoints can focus on the important structural features or the region of interest in volume data and exhibit definite correlation with the perception character of human visual system. Compared with the methods based on PSO or NM simplex search, our method has the better performance of convergence rate, convergence accuracy and robustness.

In this paper, a novel human visual sensitivity measurement approach is presented to assessment the visual quality of JPEG-coded images without reference image. The key features of human visual sensitivity (HVS) such as edge amplitude and length, background activity and luminance are extracted from sample images as input vectors. SVR-NN was used to search and approximate the functional relationship between HVS and mean opinion score (MOS). Then, the measuring of visual quality of JPEG-coded images was realized. Experimental results prove that it is easy to initialize the network structure and set parameters of SVR-NN. And the better generalization performance owned by SVR-NN can add the new features of the sample automatically. Compared with other image quality metrics, the experimental results of the proposed metric exhibit much higher correlation with perception character of HVS. And the role of HVS feature in image quality index is fully reflected.