Retrieving Keywords in Historical Vietnamese Stele Images Without Human Annotations

Stone engravings on Vietnamese steles are an invaluable resource for historians to study the life of the villagers in the past. Thanks to pictures taken of stampings of the steles, they can be investigated today in the form of digital images. Automatic keyword spotting is a promising means to access the textual content of the images, allowing to retrieve steles that contain a certain query term. In this paper, we present a complete pipeline for retrieving Chu Nom characters in Vietnamese steles that operates fully automatically on the original images, without the need for preprocessing, segmentation, or human annotation. It combines a self-calibration approach to character detection using deep convolutional neural networks with a graph-based approach to keyword spotting that compares templates of the search term with detected characters based on structural properties.