Medieval paper, a handmade product, is made with a mould which leaves an indelible imprint on the sheet of paper. This imprint includes chain lines, laid lines and watermarks which are often visible on the sheet. Extracting these features allows the identification of paper stock and gives information about chronology, localisation and movement of books and people. Most computational work for feature extraction of paper analysis has so far focused on radiography or transmitted light images. While these imaging methods provide clear visualisation for the features of interest, they are expensive and time consuming in their acquisition and not feasible for smaller institutions. However, reflected light images of medieval paper manuscripts are abundant and possibly cheaper in their acquisition. In this paper, we propose algorithms to detect and extract the laid and chain lines from reflected light images. We tackle the main drawback of reflected light images, that is, the low contrast attenuation of lines and intensity jumps due to noise and degradation, by employing the spectral total variation decomposition and develop methods for subsequent line extraction. Our results clearly demonstrate the feasibility of using reflected light images in paper analysis. This work enables the feature extraction for paper manuscripts that have otherwise not been analysed due to a lack of appropriate images. We also open the door for paper stock identification at scale.
翻译:中世纪纸是一种手工制作的产品,用一个模版制成,在纸板上留下一个不可磨灭的印记。这个模版包括链条、铺设的线条和水印,在纸板上经常可以看到。摘取这些特征可以识别纸本,提供有关书本和人的时间顺序、本地化和移动的信息。大多数纸面分析特征提取的计算工作迄今为止都侧重于放射法或传送的光图像。虽然这些成像方法为人们感兴趣的特征提供了清晰的视觉化,但它们在购买时费用昂贵和耗时,对较小的机构来说不可行。然而,反映的中世纪纸手稿的光照非常丰富,而且可能更便宜。在本文件中,我们提出算法,从反映的光图中探测和提取板条线条和链条线条。我们处理反射光图像的主要图解析,即线条的强度和强度因噪音和退化而跳动的低对比,方法是利用光谱全变变变变变法,并开发随后的线提取方法。我们的结果清楚地表明,在购买纸本分析时使用反光照片的可行性。我们建议用算图纸本进行适当的分解。我们还分析,这样就可以适当分析。</s>