Resumo
Historical archives hold vast collections of documents written with iron gall ink which have seen their legibility compromised due to multiple factors: fading and corrosion of the ink, water and mould stains, soot deposition, redactions & censorship, and so on. Physical treatment of these documents is often beyond the organisations´ resources and the capacity of conventional conservation methods. In the framework of the project “Museum of the Invisible”, digital recovery of documents legibility by means of advanced image acquisition and processing methods is explored. Both mock-up samples of inks on paper and parchment and historical documents with readability problems are examined with a range of imaging techniques, namely: multiband imaging (MBI)/technical photography (TP), hyperspectral imaging (HSI)/reflectance imaging spectroscopy (RIS), X ray fluorescence (XRF) imaging and Raman imaging. The images are then further processed to create false colour images, with Principal Component Analysis (PCA) or other methods.This poster presents, discusses and evaluates the results obtained, with a special focus on the challenge of reading strikethrough text in redacted documents, suggesting the most adequate imaging and processing approaches, in function of the materials present, as well as the type and degree of obscuring of the writing. ReferencesM.J. Melo, et al., 2022. Herit. Sci., 10 (1), 145.M. Perino, et al. 2024. Heritage, 7, 683–696. L. Pereira-Pardo et al., 2024. CULHER, 68, 342-353.
Palabras chave
Strikethrough text. Redacted documents. Multiband imaging (MBI). Hyperspectral imaging (HSI)/ reflectance imaging spectroscopy (RIS). X Ray Fluorescence (XRF) imaging. Raman imaging. False Colour images. Principal Component Analysis (PCA).