Region of interest signalling for encrypted JPEG images

We propose and evaluate different methods to signal position and size of encrypted RoIs (Regions of Interest) in JPEG images. After discussing various design choices regarding the encoding of RoI coordinates with a minimal amount of bits, we discuss both, existing and newly proposed approaches to signal the encoded coordinates inside JPEG images. By evaluating the different signalling methods on various data sets, we show that several of our proposed encoding methods outperform JBIG in this special use case. Furthermore, we show that one of our proposed signalling methods allows length-preserving lossless signalling, i.e., storing RoI coordinates in a format-compliant way inside the JPEG images without quality loss or change of file size.