纸张表面性能与硬拷贝水印提取质量相关性研究

测量7种纸张的表面性能(白度、粗糙度及平滑度、光泽度及不透明度);通过静电数码印刷机,将嵌入离散余弦变换(DCT)水印的载体图像在7种纸张上完成印刷输出;利用扫描仪获取不同分辨率下的提取水印图,并确定最适用扫描参数;选用归一化相关系数(NC值)作为水印提取质量的表征参数,并结合Pearson相关性统计分析理论,分析纸张表面性能对硬拷贝水印提取质量的影响。结果表明,纸张白度、粗糙度及平滑度与NC值的相关性均大于0.8,光泽度与NC值的相关性略大于0.6,不透明度与NC值的相关性小于0.4,说明前3个影响因素对水印提取质量的影响显著,光泽度的影响中等偏大,不透明度的影响较小;该研究为水印硬拷贝输出前的选纸工作提供了指导依据,能有效提高水印提取质量,进一步拓展水印在包装防伪中的应用。

Research on Correlation between Paper Surface Characteristics and Hard CopyWatermark Extraction Quality

Measuring the basic surface properties of 7 kinds of paper,then the carrier image embedded with the DCT watermark was printed on the 7 kinds of papers through the electrostatic digital printing machine.The extracted watermark images with different resolutions was obtained by using a scanner,and the most suitable scanning parameters was determined.The normalized correlation coefficient(NC value)was selected as the characterization parameter of watermark extraction quality.Combined with Pearson correlation statistical analysis theory,the effect of paper surface parameters on the extraction quality of hard copy watermark was evaluated.The results showed that the correlations between paper whiteness,roughness,smoothness and NC value were greater than 0.8,the gloss correlation value was slightly greater than 0.6,and the opacity value was less than 0.4.So the first three influencing factors had a strong correlation with the quality of watermark extraction,the influence of gloss was medium strong,and the influence of opacity was small.This study provided a guiding basis for paper selection before watermark hard copy output,which could effectively enhance the quality of watermark extraction and further expanded the application of watermark in packaging anti-counterfeiting.