Dense Correspondences and Ancient Texts

This chapter concerns applications of dense correspondences to images of a very different nature than those considered in previous chapters. Rather than images of natural or man-made scenes and objects, here, we deal with images of texts. We present a novel, dense correspondence-based approach to text image analysis instead of the more traditional approach of analysis at the character level (e.g., existing optical character recognition methods) or word level (the so called word spotting approach). We focus on the challenging domain of historical text image analysis. Such texts are handwritten and are often severely corrupted by noise and degradation, making them difficult to handle with existing methods. Our system is designed for the particular task of aligning such manuscript images to their transcripts. Our proposed alternative to performing this task manually is a system which directly matches the historical text image with a synthetic image rendered from the transcript. These matches are performed at the pixel level, by using SIFT flow applied to a novel per pixel representation. Our pipeline is robust to document degradation, variations between script styles and nonlinear image transformations. More importantly, this per pixel matching approach does not require prior learning of the particular script used in the documents being processed, and so can easily be applied to manuscripts of widely varying origins, languages, and characteristics.