Towards Forensic Exploitation of 3-D Lighting Environments in Practice

Abstract

The goal of image forensics is to determine authenticity and origin of a digital image or video without an embedded security scheme. Among the existing methods, the probably most well-known physics-based approach is to validate the distribution of incident light on objects of interest. Inconsistent lighting environments are considered as an indication of image splicing. However, one drawback of this approach is that it is quite challenging to use it in practice. In this work, we propose several practical improvements to this approach. First, we propose a new way of comparing lighting environments. Second, we present a factorization of the overall error into its individual contributions, which shows that the biggest error source are incorrect geometric fits. Third, we propose a confidence score that is trained from the results of an actual implementation. The confidence score allows to define an implementation- and problem-specific threshold for the consistency of two lighting environments.