Fundamentals and Applications of Hardcopy Communication

This book discusses techniques to convey side information over a printed media. Those techniques will be referred to as hardcopy communication techniques. The information is modulated over the digital host document and then printed using laser, inkjet printer technologies or other printing/branding processes. In order to recover the information at receiver side, the printed document or branded product is digitalized using either cameras or desk scanners and the resulting digital image is processed to decode the embedded information. The embedded information can be exploited for a variety of applications: document, user and/or content authentication, copyright protection, piracy deterrent, document tracking and other uses.

The literature presents an extensive research on digital watermarking applications with digital image, speech, music and video media. However, much less research effort has been applied to hardcopy communication via printed media. Hardcopy images can be used to convey side information required for many security, tracking, copyright and forensic applications. Many office applications rely on a tight connection between physical and electronic documents. Physical (printed) images can be a token for the electronic document (or documents) it represents directly (or indirectly as part of a shared workflow). Hiding information in images to be printed can be used to embed side information or to save real estate on the label, document or packaging printed media. This hidden information is useful for location-based services, point-of-sale, security, counterfeit and piracy deterrence, content authentication, fingerprinting and more. Depending on the application different approaches to address encoding, modulation, and detection of information are required to achieve a given tradeoff among payload, transparency and robustness. This chapter discusses state-of-the-art approaches for hardcopy image communication, describes main sources of distortion in the black-and-white and color print-scan channels, discusses resulting performance of alternative encoding, modulation and detection techniques.

This chapter discusses one type of overt (visible) communication by employing color print codes aiming to convey information over printed media. In the literature many print codes have been proposed for conveying information, ranging from simple shapes like the PARC (Palo Alto Research Center Incorporated) dataglyphs, the popular linear-1D and 2D barcodes [11] to the recent color barcodes or 3D barcodes such as the Microsoft High Capacity Color Barcode (HCCB). However, communication systems that require screen displays such as the 4D barcodes [7] are not considered.