A geometric-based tattoo retrieval system

Various soft biometric traits have been used as hints in forensic investigation. Tattoo, as one of those soft biometric traits, has been used extensively because it is easy to be remembered and described by witnesses and appears very often among criminals and victims. Most of the tattoo retrieval systems currently used in police departments are still text-based systems. They depend on labels tagged on the tattoo images in databases. This manual labelling process is very time consuming and subject to loss of some detailed information, such as the accurate location and the shape of tattoos. These problems can make tattoo retrieval inefficiently and misleading. To address them, a geometric based tattoo retrieval system is developed. It allows witnesses to draw the boundary of a query tattoo and retrieve all the tattoos with similar shape around the particular location. The system comprises a tattoo detection algorithm, which detects tattoos from full body images, a full body coordinate algorithm, which defines locations of input tattoo boundaries and locations of tattoos in databases and a tattoo shape matching algorithm, which measures similarity between input boundaries and boundaries of tattoos in databases. The experimental results on 2188 images show the effectiveness of the proposed system.