后处理在数字抠像中的应用与解析

数字抠像是将一幅图像中的前景物体与背景进行分离的问题,它的关键在于Alpha通道的计算.以往通过采样方法求得的Alpha中,由于采用逐点计算的离散化方式,求解出的Alpha通常不连续,并且包含很多噪声,因而需要对Alpha进行后处理,这不仅会增强Alpha在视觉上的平滑性,而且能够进一步提高Alpha的精确度.在目前国际上,有关数字抠像后处理领域已经进行了许多研究,但缺少相关的综述性文献,并且对后处理后的Alpha如何进行定量的评价也仍未系统解决.本文首先将数字抠像中的后处理方法分为2类:与仿射类方法相结合的方式及自平滑方式,其次,对两类方法进行了全面的总结和梳理,并对方法的优缺点进行了分析,对将来研究方向提出了建议,最后,针对后处理后的Alpha结果进行了全面的量化比较,弥补了传统方法基本上仅在视觉层面上进行比较的缺陷.

Applications and Analyses on Post Processing in Image Matting

Image matting is a process which separates the foreground object from the background scene,and the key of matting is to compute the alpha matte.The existing sampling based matting methods are always in a discretized strategy,which could results in a great deal of discontinuities and noises in final alpha mattes.Post processing is thus introduced to enhance the smoothness and to further increase the accuracy of the final matte.However,the corresponding review articles are still lacking in the field of intemational research of post-processing in image matting.Moreover,the quantitative evaluation of alpha mattes still remains unsolved.This paper firstly classifies the post-processing step into two basic categories:affinitycombined and self-smoothing.Next,the advantages and disadvantages are both summarized and analyzed.Finally,the alpha mattes after post-processing are evaluated in quantitative manner comprehensively,which improves the problem of pure visual evaluation in traditional methods.