Uncovering the underdrawings (UDs), the preliminary sketch made by the painter on the grounded preparatory support, is a keystone for understanding the painting's history including the original project of the artist, the pentimenti (an underlying image in a painting providing evidence of revision by the artist) or the possible presence of co-workers' contributions. The application of infrared reflectography (IRR) has made the dream of discovering the UDs come true: since its introduction, there has been a growing interest in the technology, which therefore has evolved leading to advanced instruments. Most of the literature either report on the technological advances in IRR devices or present case studies, but a straightforward method to improve the visibility of the UDs has not been presented yet. Most of the data handling methods are devoted to a specific painting or they are not user-friendly enough to be applied by non-specialized users, hampering, thus, their widespread application in areas other than the scientific one, e.g., in the art history field. We developed a computer-assisted method, based on principal component analysis (PCA) and image processing, to enhance the visibility of UDs and to support the art-historians and curators' work. Based on ImageJ/Fiji, one of the most widespread image analysis software, the algorithm is very easy to use and, in principle, can be applied to any multi- or hyper-spectral image data set. In the present paper, after describing the method, we accurately present the extraction of the UD for the panel "The Holy Family with St. Anne and the Young St. John" and for other four paintings by Luini and his workshop paying particular attention to the painting known as "The Child with the Lamb".

中文翻译：

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EXPRESS：“圣安妮和年轻的圣约翰的神圣家庭”的幕后花絮，作者 Bernardino Luini：一种计算机辅助的方法来揭开底图的面纱

Uncovering the underdrawings (UDs) 是画家在接地的准备支撑上绘制的初步草图，是了解这幅画的历史的基石，包括艺术家的原始项目，pentimenti（一幅画中的底层图像，提供了修改的证据）艺术家）或可能存在同事的贡献。红外反射成像 (IRR) 的应用使发现 UD 的梦想成真：自推出以来，人们对该技术的兴趣日益浓厚，因此该技术已发展为先进的仪器。大多数文献要么报告了 IRR 设备的技术进步，要么介绍了案例研究，但尚未提出一种直接的方法来提高 UD 的可见性。大多数数据处理方法专门针对特定的绘画，或者它们不够用户友好，无法由非专业用户应用，因此阻碍了它们在科学领域以外的领域的广泛应用，例如艺术史场地。我们开发了一种基于主成分分析 (PCA) 和图像处理的计算机辅助方法，以提高 UD 的可见性并支持艺术史学家和策展人的工作。该算法基于最流行的图像分析软件之一 ImageJ/Fiji，非常易于使用，原则上可以应用于任何多光谱或高光谱图像数据集。在本文中，在描述了该方法之后，我们准确地呈现了面板“The Holy Family with St. Anne and the Young St. John”的 UD 提取