3D remote colorimetry and watershed segmentation techniques for fresco and artwork decay monitoring and preservation

摘要

One of the most crucial problems in cultural heritage environment is the remote monitoring of the state of monuments, especially of large surfaces (e.g. frescos, chapels). In 2011 a complete 3D colour digitization of the Sistine Chapel was executed by the RGB-ITR (Red Green Blue - Imaging Topological Radar) laser scanner prototype, developed by the UTAPRAD-DIM (Technical Unit for the development of APplications of RADiations - Diagnostics and Metrology) lab of C.R. ENEA Frascati. The preservation of the frescos is put at risk by the salt efflorescence (e.g., calcium carbonate) due to physical and chemical agents. These outcrops showing colours deterioration appear on the fresco as whitish areas of variable size. Within this framework, the scientific challenge is to provide a starting point for the non-invasive diagnosis of fresco degradation in order to contribute to the design and realization of innovative solutions for the restoration and conservation of the paintings, especially in presence of extended surfaces with difficult access. The present work shows the results obtained by the integration of two techniques, based on the RGB-ITR hyper-photos and the watershed algorithm for a semi-automatic detection of defects on fresco. The study case concerns the fresco located inside the Sistine Chapel known as "Temptations of Christ" by Sandro Botticelli.