Learning based Word Search and Visualisation for Historical Manuscript Images

Abstract: Today, work with historical manuscripts is nearly exclusively done manually, by researchers in the humanities as well as laypeople mapping out their personal genealogy. This is a highly time consuming endeavour as it is not uncommon to spend months with the same volume of a few hundred pages. The last few decades have seen an ongoing effort to digitise manuscripts, both preservation purposes and to increase accessibility. This has the added effect of enabling the use methods and algorithms from Image Analysis and Machine Learning that have great potential in both making existing work more efficient and creating new methodologies for manuscript-based research.The first part of this thesis focuses on Word Spotting, the task of searching for a given text query in a manuscript collection. This can be broken down into two tasks, detecting where the words are located on the page, and then ranking the words according to their similarity to a search query. We propose Deep Learning models to do both, separately and then simultaneously, and successfully search through a large manuscript collection consisting of over a hundred thousand pages.A limiting factor in applying learning-based methods to historical manuscript images is the cost, and therefore, lack of annotated data needed to train machine learning models. We propose several ways to mitigate this problem, including generating synthetic data, augmenting existing data to get better value from it, and learning from pre-existing, partially annotated data that was previously unusable.In the second part, a method for visualising manuscript collections called the Image-based Word Cloud is proposed. Much like it text-based counterpart, it arranges the most representative words in a collection into a cloud, where the size of the words are proportional to their frequency of occurrence. This grants a user a single image overview of a manuscript collection, regardless of its size. We further propose a way to estimate a manuscripts production date. This can grant historians context that is crucial for correctly interpreting the contents of a manuscript.