**Abstract**

This chapter describes how optical information and advanced image processing can be used to study archeological objects and artworks in order to determine more precisely and noninvasively the characteristics of the shape and color of artifacts. The purpose of this research is to develop a passive experimental technique for artifact investigation to help human experts make the best decisions in the process of authenticating and preserving-restoring objects. The method used is digital capture of object images followed by processing them with specialized software tools to analyze the chromatic characteristics and apparent geometric details. The proposed methodology consists of intelligently combining digital image analysis functions to build a set of chromatic-structural features useful for recognizing possible differences and estimating color and shape evolution. The investigation of the artifacts through digital image processing is a noninvasive and precise complementary method of analysis that can reduce the costs, and it must be extensively integrated into decision support systems for experts and curators in the field of artistic heritage preservation.

**Keywords:** digital image analysis, artifact authentication, conservation-restauration

### **1. Introduction**

Conservation, restoration, and authentication of artifacts are activities performed by human experts using a multidisciplinary set of knowledge and corroborating information obtained through advanced investigation techniques. In general, human experts rely on their own skills of recognizing the composition of works of art using complex cognitive processes of interpretation of forms, colors, and textures in correlation with information about the technique of realization of the work being analyzed. Artifacts are important and valuable in their appearance, but this is affected by the passing of time, environmental physical parameters, as well as other natural or man-made causes. In current activities of authentication, conservation, and restoration, human experts are increasingly being helped by technical methods involving invasive and noninvasive analyses.

Optical information provides essential data about the appearance of objects and plays a major role in classifying them. The apparent representation of objects is perceived by the visual system through shape and color features. The shape of an object is determined by the spatial relationship between the points defining its visible surface, while the color of each point is determined by the punctual interaction of the object with the optical radiation in the external environment. Between these two basic features of objects, there is a univocal relationship, meaning that the shape of objects can influence the perceived color, but not vice versa. The shape and color of objects can be assessed generally by geometric measurements or photometric techniques. Experimental methods are most effective in obtaining data to the extent that they do not affect the artifact. Optical scanning is a passive experimental technique, considered noninvasive, excepting the particular situations where artifacts may deteriorate due to exposure to light.

Based on the optical methods, quantitative and qualitative analyses can be made on the shape and chromaticity of artifacts of any kind such as distinct archeological pieces, stamps, paintings, and other forms of decorative art like mosaics, engravings, embroideries, and artistic upholstery. Image analysis models include special mathematical functions for calculating conventional measures to characterize shapes and parameters for color evaluation. Digital image processing is widely used in everyday life with many applications in the industry, health, transport, telecommunications, social security, and military. This chapter discusses the applicative features of digital image processing in the field of artistic and historical heritage protection by proposing complementary image-based analysis techniques for a better investigation of artifacts. The concepts discussed are supported by some applicative examples. The scientific purpose of this methodology is to obtain a relevant structural-chromatic set of features for an artifact at a certain time.
