Analysis and Improvement of Formulas for Evaluating Similarity Degree of Digital Watermarks
评价数字水印相似程度的公式分析及改进

Currently familiar formulas called normalized cor- relation,which are used for evaluating the similarity degree of digital watermarks,showed their big shortage when expressing the similarity degree of extracted watermark and original wa- termark in inverse similarity.Therefore,in this paper,several common formulas of normalized correlation are analyzed firstly. Then by inheriting the rationality and effectivity of these formu- las,and overcoming the shortage of them,a novel formula named polarized correlation is constructed,which can more scientifi- cally,rationally,and effectively evaluate the similarity degree of digital watermarks.Lastly,contrasting experiments of polarized correlation and normalized correlation are done,and the experi- mental results validate the science,rationality,and effectivity of polarized correlation.