RE-SEQUENCING A HISTORICAL PALM LEAF MANUSCRIPT WITH BOUNDARY-BASED SHAPE DESCRIPTORS (original) (raw)

2003, 19th CIPA International Symposium, Antalya, Turkey, September 30-October 4. International Archives of the Photogrammetry, Remote Sensing and Spatial Information Sciences, vol. XXXIV, part 5/C15, pp. 55-60.

ABSTRACT: A stack of 66 historical Indian palm leaves, which were produced in the 8th Century AD, is kept in the Museum Rietberg, Zuerich. On the leaves, there are figures and a long poem, inscribed in ancient Sanskrit language and narrating a love story. The original sequence of the leaves was lost long time ago. At one point in history, the stack of the leaves was damaged by a mouse biting pieces off. Only the first 18 leaves have their pages numbered in Sanskrit language, but the rest of them got out of order. If it is assumed that the mouse chewed at the leaves in a regular manner, the geometry of the leaf perimeter, as left over after eating, should bear useful information to find the original sequence. After acquiring digital images of the leaves and a pre-processing phase, an inner boundary-tracing algorithm was applied to all leaves in order to segment them. The fundamental data used in this work are boundary coordinates of the leaves. In order to obtain quantitative shape similarity measures, two different Boundary Based Shape Descriptor algorithms were applied to the boundary data: Fourier descriptors and a rotation-translation invariant boundary intersection-based shape descriptor. Shape descriptors indicate the similarity of different leaves. These similarity measures among all of the leaf pairs were arranged in form of a symmetric square matrix. With this matrix and a threshold similarity value one can determine the most probable ancestor and successor leaves for a pointed leaf. In the final step, a Tree Search scheme that starts from the 18th (fixed) leaf and ends at the 66th (relaxed) leaf was established to generate the most probable sequence. Every node in the tree was defined as a leaf and branched to the most probable neighbor leaves. The similarity measures were expressed as costs of the arcs, which connect two nodes in the tree. The sequence which has minimum total path cost was proposed as the most probable original sequence. KEY WORDS: Cultural Heritage, Image Analysis, Boundary-tracing, Fourier descriptors, shape similarity measures, Tree-Search, Visualization