An Optical Watermarking Solution for Color Personal Identification Pictures

TL;DR

This paper introduces an optical watermarking technique for personal identification images, embedding invisible digital watermarks into printed photos using a projector-camera setup, enhancing security against forgery.

Contribution

It presents a novel optical projection-based watermarking method that embeds and detects watermarks in printed images, improving robustness over traditional digital techniques.

Findings

Watermarks are embedded into the blue channel of color images.

The watermark is detectable via optical and digital correlation methods.

The approach is resistant to forgery, printing, and scanning modifications.

Abstract

This paper presents a new approach for embedding authentication information into image on printed materials based on optical projection technique. Our experimental setup consists of two parts, one is a common camera, and the other is a LCD projector, which project a pattern on personnel's body (especially on the face). The pattern, generated by a computer, act as the illumination light source with sinusoidal distribution and it is also the watermark signal. For a color image, the watermark is embedded into the blue channel. While we take pictures (256 *256 and 512*512, 567*390 pixels, respectively), an invisible mark is embedded directly into magnitude oefficients of Discrete Fourier transform (DFT) at exposure moment. Both optical an d digital correlation is suitable for detection of this type of watermark. The decoded watermark is a set of concentric circles or sectors in the DFT domain (middle frequencies region) which is robust to photographing, printing and scanning. The unlawful people modify or replace the original photograph, and make fake passport (drivers' license and so on). Experiments show, it is difficult to forge certificates in which a watermark was embedded by our projector-camera combination based on analogue watermark method rather than classical digital method.