Digital image watermarking techniques

Abstract

The ability to resolve ownership disputes and copyright infringement is difficult in the worldwide digital age. There is an increasing need to develop techniques that protect the owner of digital data. Digital Watermarking is a technique used to embed a known piece of digital data within another piece of digital data. The embedded piece of data acts as a fingerprint for the owner, allowing the protection of copyright, authentication of the data, and tracing of illegal copies. The goal of this thesis is to produce two watermarking tools and compare their effectiveness with that of other watermarking tools. One of the tools uses a spatial watermarking technique, while the other uses a frequency based spread spectrum technique. These represent the two current approaches to digital watermarking. Use of a standard benchmark is necessary to advance the science of digital watermarking. Until recently, there have been no standard metrics for deter mining the effectiveness of a particular watermarking scheme. Several recent papers propose standard procedures and metrics for comparing watermarking techniques. The proposed metrics and test bed imagery are used as the basis for comparison with other watermark techniques. Overall, the most successful techniques model themselves after data communications techniques. In this case, the image is similar to the atmosphere (medium) and the watermark message is the signal communicated through the medium. The spread spectrum technique yields results that in some cases are comparable to commercial watermarking tools. The spatial domain tool as implemented is inadequate for comparison with the commercial tools