Restoring ink bleed-through degraded document images using a recursive unsupervised classification technique

This paper presents a new method to restore a particular type of degradation related to ancient document images. This degradation, referred to as "bleed-through", is due to the paper porosity, the chemical quality of the ink, or the conditions of digitalization. It appears as marks degrading the readability of the document image. Our purpose consists then in removing these marks to improve readability. The proposed method is based on a recursive unsupervised segmentation approach applied on the decorrelated data space by the principal component analysis. It generates a binary tree that only the leaves images satisfying a certain condition on their logarithmic histogram are processed. Some experiments, done on real ancient document images provided by the archives of "Chatillon-Chalaronne" illustrate the effectiveness of the suggested method.