Characterization of Prints Based on Microscale Image Analysis of Dot Patterns

Identifying a print document (original) from a reprint document (copy or fake) can be a challenge. The analyse at microscopic scale of print documents shows random dot shapes which depend on the printing parameters as well as the printing device used. We can, therefore, draw the assumption that the dot shapes can be used as a fingerprint to differentiate a print from a reprint. In this paper, we explore several shape indexes that were not investigated until now to analyse at microscopic scale documents printed on aluminium foils using rotogravure printing process. This paper presents a statistical analysis which is based on a pattern recognition process defined by three steps. First, a new image processing pipeline is used to segment automatically disconnected dots. Next, new dot pattern features are used to characterize automatically dot patterns. Six types of dot patterns (including four types of doughnut patterns) are introduced. Lastly, a new statistical analysis method is used to characterize a printed sample from the set of dots printed on it. The experiments done demonstrate the relevance of the analytical method proposed. Results shows the potential of this method to identify a reprint from a print.