{'fraction_non_alphanumeric': 0.013210798391728892, 'fraction_numerical': 0.0022975301550832855, 'mean_word_length': 5.243727598566308, 'pattern_counts': {'":': 0, '<': 0, '<?xml version=': 0, '>': 0, 'https://': 0, 'lorem ipsum': 0, 'www.': 0, 'xml': 0}, 'pii_count': 0, 'substrings_counts': 0, 'word_list_counts': {'cursed_substrings.json': 0, 'profanity_word_list.json': 0, 'sexual_word_list.json': 0, 'zh_pornsignals.json': 0}}
Fragment similarity evaluation in virtual aided recomposition of frescos

The goal of our work is the development of a system for the virtual aided recomposition of frescos. The system is intended to be applied to the St Matthew's fresco, painted by Cimabue in the Upper Church of St Francis in Assisi and fragmented during the earthquake on September 1997. The high number of fragments, the necessity of avoiding further damages caused by physical manipulation and the opportunity of coordinating the work of several operators while increasing their efficiency suggest the use of the virtual modality. On the other hand the intrinsic characteristics of the digital images (providing insufficient information for finding automatically the correct location of each fragment inside the fresco) prevent the possibility of a fully autonomous system. Humans and digital system must therefore work together in order to optimally accomplishing the task. A key aid to the operators is the retrieval of fragments similar to suitably chosen examples. Unfortunately, the acquisition set-up of the available image of the whole fresco (type of camera, light and geometry) is completely unknown. Even the acquisition of fragments has produced images that are not homogeneous in terms of luminance. The similarity function between images must account for these problems in order to provide an effective help to the operators. The results obtained using an illuminant invariant algorithm for the comparison of images, the Color Angular Indexing will be described. This algorithm has performed well in several different tests, returning reliable similarity estimations on images of fragments in spite of rotations as far as changes in scale and illumination.