How to Read the Unreadable? Non-Invasive digitization of cultural heritage

Speakers: Vincent Christlein (Friedrich-Alexander University) @v_christlein
Daniel Stromer (Friedrich-Alexander University) @daniel_stromer

Sealed documents can contain valuable sources of information. In this presentation, we will give an overview of our efforts in reading sealed documents. These may be books or scrolls that have been damaged by external influences (e.g., fire, water) or are too fragile to open them due to aging processes. We show that non-invasive methods, such as 3-D X-ray computed tomography (CT) imaging, are capable of revealing hidden contents. We outline the full pipeline of the digitization process: first the document is scanned by means of CT imaging. Afterwards, the pages need to be extracted. Due to the high resolution and the thin and wavy pages, which are also squeezed together, the separation of pages within the 3-D volume is not trivial. Since manual segmentation is too time-consuming, a fully automated process for extracting and mapping the pages in 2-D was developed. While a large proportion of documents were written with iron gall ink, other inks were also used. Therefore, we evaluated which inks could be reliably made visible. In contrast to codices, books or manuscripts, symbols and drawings were captured on bamboo in ancient China. Wooden slips were used as the common communication media. Unfortunately, the discovered pieces are sometimes in a poor condition and contaminated by soil. The manual cleaning of excavated slips is a demanding and time-consuming task in which writings can be accidentally erased. Therefore, we are investigating the possibility of using also CT imaging for digitization. We propose a mainly automatic algorithmic solution to virtually clean the bamboo scrolls from contaminated soil. Then, the scroll is digitally unwrapped and the 3-D slips are processed in a texturing step to obtain a 2-D representation readable by the naked eye. This digitization also allows the recovery of potentially erased writings and reconstruction of the original spatial information. Eventually, we will discuss the potential and challenges of using CT for a broad application of the technique.

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