The combination of imaging technique, lighting, filters and subsequent image processing allows for a restoration of legibility of fire-damged or water-damaged or faded documents. A multi-spectral digitization with optimum contrast can be carried out by using light spectrums suitable for the respective type of damage of the original fragments. In the case of fire damage, lighting in the visible and the infrared range is suitable. In the case of damage by extinguishing water lighting in the visible and the ultraviolet range is used.
Automated processes of image processing and pattern recognition are then employed to interpret the recorded digital image data. Textual information can, for example, be highlighted by means of a separation of foreground and background information or by an improvement of the text-background contrast. This way, text information can be automatically extracted from the optimized digital copy and separated from the background, which can, in most cases, digitally compensate for the existing text loss in the original documents.
Finally, the image processing results of text documents that are digitally restored to legibility can be visualized for further scientific use or public presentations. The results can be graphically displayed on a neutral background or enlarged in sections for a detailed view. It is also possible to overlay the restored text on top of the damaged original.
The process of restoring legibility has already been applied to sheet music manuscripts damaged by fire and water in a project with Classic Foundation Weimar / Duchess Anna Amalia Library. Article on the subject