Digital image watermarking in transform domian

Abstract

Visual Cryptographic methods are not sufficient to solve all image security related issues. Watermarking is the art of hiding secret image in ways that prevent the detection of hidden images. Multimedia documents are very easy to copy and distribute in an illicit manner. Copyright labelling is a process that may help to reduce their illicit copying. If this document is copied the copy will also contain the label. This label (or watermark) should be robust enough to withstand normal image processing activities (like image compression, transforming to different format) that do not significantly alter the image appearance. In fractal image compression the encoding step is computationally expensive, because every range block must be compared to all domain blocks in the codebook to find the best-matched one during the coding procedure. In this paper, a fast fractal encoding algorithm is proposed. Simulation results show that the runtime of the proposed algorithm is reduced greatly compared to the existing methods. At the same time, the new algorithm also achieved high compression ratio.