Image analysis – Applications
Reexamination Certificate
1999-03-19
2001-06-12
Johns, Andrew W. (Department: 2621)
Image analysis
Applications
Reexamination Certificate
active
06246777
ABSTRACT:
DESCRIPTION
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention generally relates to a verification system for still images and, more particularly, to a technique that embeds a watermark so that no visual artifacts are created in the image.
2. Background Description
Watermarking is seen as a viable solution for the authentication of multimedia data and hence its security. Because of the huge size, color images as well as grey-scale images are usually kept in some standard compressed format, e.g., JPEG (Joint Photographers Experts Group). An imperceptible watermark (or watermark, for short) is defined as an alteration of the data set that is not perceptible to a human, but can be recognized by a machine such as a computer or a pervasive computing device.
SUMMARY OF THE INVENTION
It is therefore an object of the present invention to provide a verification system for still images that embeds a watermark so that no visual artifacts are created in the images, and the visual quality of the image is thus maintained.
According to the invention, there is provided an algorithm to embed information in an uncompressed image so as to later detect the alteration of the image, as well as the location of the alteration. The embedding of information into a source image is based on a defined mapping process; this information can be later decoded from the stamped image. The watermark is embedded by combining the pixel values of the image with the watermark. So if an attempt is made to alter the image, the watermark is also altered and the alteration of the watermark is captured during the verification process.
This invention provides a novel, low-overhead, watermarking scheme which, in most practical cases, offers an invisible watermark capable of detecting any significant tampering of the image content, and immune to lossy compression schemes such as JPEG. The watermarking technique according to the invention is based on certain empirically verified attributes of an image property; e.g., average intensity value.
Assume an image plane consists of macroblocks, which are themselves made up of microblocks. In its preferred embodiment, a code is embedded that corresponds to the value of this image property in each macroblock, in spatial domain. The specific sequence of microblocks used for embedding this information in the watermarking image plane is a unique function of this property for the corresponding set of microblocks in the indexing image plane. This offers sensitivity to alterations as well as immunity from brute-force efforts for watermark extraction.
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“Transform permuted watremarking for copyright protection of digital video” by Johnson et al., IEEE, Globecom, Nov. 8, 1998.
Agarwal Saurabh
Aggarwal Alok
Bassali Harpal Singh
Chhugani Jatin
Dubey Pradeep Kumar
International Business Machines - Corporation
Johns Andrew W.
Kaufman, Esq. Stephen C.
McGuireWoods LLP
Nakhjavan Shervin
LandOfFree
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