Towards copy-evident JPEG images

Abstract: We present a technique for adding a high-frequency pattern to JPEG images that is imperceptible to the unaided eye, but turns into a clearly readable largeletter warning if the image is recompressed with some different quality factor. Our technique aims to achieve a goal similar to copy-evident security-printing techniques for paper documents, namely to have an easily recognizable text message appear in lower-quality copies, while leaving the visual appearance of the original unharmed. We exploit non-linearities in the JPEG process, in particular the clipping of the result of the inverse discrete cosine transform.

• Type: Conference
• Year: 2009
• Where: GI
• Authors: Andrew Lewis, Markus Kuhn
• Keywords: GI 2009, Inverse Discrete Cosine, Recognizable Text Message, Theoretical Computer Science, Unaided Eye