Study On The Image Enhancement Based On The Human Vision Property

Image enhancement could achieve a better visual effect and improve the human eye's ability to identify information. Moreover, as a preconditioning technique, it can make the processed images more suitable than the original ones to do the following analysis such as parameter estimation, image segmentation, object recognition and so on. Thus, the study on enhancement has always been being one of the main contents in image processing field. However, the traditional image enhancement algorithms based on histogram have several shortcomings. 1) The information carried by gray levels is inconsistent with its statistic data in conventional histogram. 2) The conventional histogram equalization has not made full use of the visual sensitive regions in the process of gray level adjustment. 3) The parameters cannot be optimized on and configured adaptively in view of the variability of the image content. To cope with these problems, the relative detailed work can be concluded as follows.First, to overcome the drawback of conventional histogram, a novel histogram construction method has been proposed based on visual attention mechanism. Both the quantity and space distribution are considered in the statistic process of gray levels. The importance of gray levels in different positions can be calculated by using the computational model of visual attention mechanism. Meanwhile, the statistic results are weighted according to the importance of every pixel. The new histogram method could reflect the influence of the gray levels on the image information objectively.Second, in order to consider the nonlinear character of visual perception in the process of gray level adjustment fully, it has been raised that different amounts of gray level information are distributed to different visual sensitive regions. The region with high sensitivity should be allocated more information. And the main gray levels are constrained by using the perception ability curve of human eyes, avoiding them occupying large space in the expanding process of histogram.Finally, in order to obtain better image enhancement results, the proportions of histogram information distributed to every visual sensitive region should be adjusted due to the variability of image content. Thus, an adaptive method to obtain the optimal regulating parameters is proposed based on the analysis of the image enhancement assessment. The quantitative evaluation method for image enhancement is designed based on the vision properties. Experiments indicate that the values of assessment approximate to those of human vision system.