Silhouette coefficient based approach on cell-phone classification for unknown source images

Cell-phones have become a necessary communication accessory in daily life. MMS (Multimedia Messaging Service) used by smart phones has caused higher requirement on mobile image manipulation. Classifying image source cell-phones has become a major issue in the cell-phone communication forensics. There are two ways usually used for tracing and identifying the source device: image characteristics and equipment fingerprint. Both of the above schemes require a set of images captured by known source cell-phones for training a classification model. To avoid using any prior knowledge in practical scenarios, a graph based approach was proposed to classify the source cell-phones. Though an acceptable result has been obtained, a problem of incomplete classification appears in the case that one image is classified wrong into a single subset. In this paper, a silhouette coefficient based algorithm is proposed for source cell-phone classification. The spectral clustering algorithm is adopted in graph partitioning and the silhouette coefficient is used to extract the optimal classification from all the possibilities of classification. Experimental results show the validity of the proposed method.