Semi-automatic system for UV images analysis of historical musical instruments

The selection of representative areas to be analyzed is a common problem in the study of Cultural Heritage items. UV fluorescence photography is an extensively used technique to highlight specific surface features which cannot be observed in visible light (e.g. restored parts or treated with different materials), and it proves to be very effective in the study of historical musical instruments. In this work we propose a new semi-automatic solution for selecting areas with the same perceived color (a simple clue of similar materials) on UV photos, using a specifically designed interactive tool. The proposed method works in two steps: (i) users select a small rectangular area of the image; (ii) program automatically highlights all the areas that have the same color of the selected input. The identification is made by the analysis of the image in HSV color model, the most similar to the human perception. The achievable result is more accurate than a manual selection, because it can detect also points that users do not recognize as similar due to perception illusion. The application has been developed following the rules of usability, and Human Computer Interface has been improved after a series of tests performed by expert and non-expert users. All the experiments were performed on UV imagery of the Stradivari violins collection stored by "Museo del Violino" in Cremona.