Browse Prior Art Database

DIGITAL WATERMARKING USING RANDOM-DOT STEREOGRAMS

IP.com Disclosure Number: IPCOM000027715D
Original Publication Date: 1999-Feb-28
Included in the Prior Art Database: 2004-Apr-09
Document File: 2 page(s) / 133K

Publishing Venue

Xerox Disclosure Journal

Abstract

Disclosed is a method of including hidden information in a halftone image with a stochastic screen. The information is normally invisible, but can be detected when viewing the halftone pattern in detail. This method is based on a random-dot stereogram and when viewed properly, a hidden code or watermark is seen as being offset in depth from the background.

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XEROX DISCLOSURE JOURNAL

DIGITAL WATERMARKING USING

Shen-ge Wang Steven J. Harrington

RANDOM-DOT STEREOGRAMS

Proposed Classification
U. S. C1. 335/181 Int. C1. G03g 15/04

Disclosed is a method of including hidden information in a halftone image with a stochastic screen. The information is normally invisible, but can be detected when viewing the halftone pattern in detail. This method is based on a random-dot stereogram and when viewed properly, a hidden code or watermark is seen as being offset in depth from the background.

It is sometimes useful to include hidden information in an image. Information such as the owner or creator of the image can be used to resolve copyright issues and inhibit illegal copying. Digital watermarks provide a method of inserting such hidden information. Methods for Watermarking continuous-tone images are known, but require examination of a digital master for detection. If an image is printed and rescanned, the watermark is lost. A watermarkjng technique based on stochastic halftone screens is also known whereby, this method inserts the watermark into the binary rendering of the image. The mark can be detected in the printed image and is preserved when copied. The watermark is normally invisible, but can be detected by comparing the image against itself. This can be done, for example, by copying the image onto a transparent medium, and overlying the copy on the original print. Shifting the copy to the proper alignment reveals the watermark. Analogous operations can be carried out in the digital domain to detect the watermark in the electronic form.

The disclosed watermarking method is also based on stochastic halftones. However, just looking at the image property reveals the normally invisible watermark. There is no need for making copies to compare the image with itself. This method uses a random-dot stereogram. The random-dot stereogram gives an illusion of three-dimensional objects when looking at a repeating texture of dots. The human brain is very good at taking the images from the left and right eye, matching the pattern seen in the two images, and determining distances from their relative angles. Nonetheless, with a repeating pattern, the brain can be tricked into matching two pattern instances that are really different. This results in a false depth reading. One can produce the effect of a foreground object nearer to the viewer from the...