Enhancement of Multispectral Images of Degraded Documents by Employing Spatial Information

Abstract

This work aims at enhancing ancient and degraded writings, which are captured by MultiSpectral Imaging systems. The manuscripts captured, contain faded out characters and are partly corrupted by mold and hardly legible. Several works have shown that such writings can be enhanced by applying unsupervised dimension reduction tools - like Principal Component Analysis (PCA) or Independent Component Analysis (ICA). In this work the Fisher Linear Discriminate Analysis (LDA) is applied in order to reduce the dimension of the multispectral scan and to enhance the degraded writings. Since Fisher LDA is a supervised dimension reduction tool, it is necessary to label a subset of multispectral data. For this purpose, a semi-automated label generation step is conducted, which is based on an automated detection of text lines. Thus, the approach is not only based on spectral information - like PCA and ICA - but also on spatial information. The method has been tested on two Slavonic manuscripts. A qualitative analysis shows, that the LDA based dimension reduction gains better performance, compared to unsupervised techniques.