Alberto Campagnolo

The value of critical destruction: Evaluating multispectral image processing methods for the analysis of primary historical texts

Multispectral imaging – a method for acquiring image data over a series of wavelengths across the light spectrum – is becoming a valuable tool within the cultural and heritage sector for the recovery and enhancement of information contained within primary historical texts. However, most applications of this technique, to date, have been bespoke: analysing particular documents of historic importance. There has been little prior work done on evaluating this technique in a structured fashion, to provide recommendations on how best to capture and process images when working with damaged and abraded textual material. This paper introduces a new approach for evaluating the efficacy of image processing algorithms in recovering information from multispectral images of deteriorated primary historical texts. We present a series of experiments that deliberately degrade samples cut from a real historical document to provide a set of images acquired before and after damage. These images then allow us to compare, both objectively and quantitatively, the effectiveness of multispectral imaging and image processing for recovering information from damaged text. We develop a methodological framework for the continuing study of the techniques involved in the analysis and processing of multispectral images of primary historical texts, and a dataset which will be of use to others interested in advanced digitisation techniques within the cultural heritage sector.

Multispectral imaging of degraded parchment

Multispectral imaging was employed to collect data on the degradation of an 18th century parchment by a series of physical and chemical treatments. Each sample was photographed before and after treatment by a monochrome digital camera with 21 narrow-band filters, with the objective of assessing algorithms for recovery of text from the images. A template-matching technique was used to detect the circular holes in each sample and a four-point projective transform to register the 21 images. Colour accuracy was verified by comparison of reconstructed spectra with measurements by spectrophotometer.

Digitally Reconstructing The Great Parchment Book: 3D recovery of fire-damaged historical documents

The Great Parchment Book of the Honourable the Irish Society is a major surviving historical record of the estates of the county of Londonderry (in modern day Northern Ireland). It contains key data about landholding and population in the Irish province of Ulster and the city of Londonderry and its environs in the mid-17th century, at a time of social, religious, and political upheaval. Compiled in 1639, it was severely damaged in a fire in 1786, and due to the fragile state of the parchment, its contents have been mostly inaccessible since. We describe here a long-term, interdisciplinary, international partnership involving conservators, archivists, computer scientists, and digital humanists that developed a low-cost pipeline for conserving, digitizing, 3D-reconstructing, and virtually flattening the fire-damaged, buckled parchment, enabling new readings and understanding of the text to be created. For the first time, this article presents a complete overview of the project, detailing the conservation, digital acquisition, and digital reconstruction methods used, resulting in a new transcription and digital edition of the text in time for the 400th anniversary celebrations of the building of Londonderry’s city walls in 2013. We concentrate on the digital reconstruction pipeline that will be of interest to custodians of similarly fire-damaged historical parchment, whilst highlighting how working together on this project has produced an online resource that has focussed community reflection upon an important, but previously inaccessible, historical text.