Watermarking on Compressed Image: A New Perspective

Watermarking is highly demanding in recent times for the protection of multimedia data in network environment from illegal copying, violation of copyright, authentication etc (Hartung & Kutter,1999), while compression of multimedia signals is essential to save storage space and transmission time. Hence, it is needless to mention the importance of watermarking on compressed data. However, the working principles of watermarking and compression seem to be different as perceptual data coding removes inherent redundancy during compression. On the other hand, watermarking uses this redundancy space for making data embedding imperceptible. As a matter of fact, watermarking on compressed data becomes more challenging, and many solutions come out as an optimization problem in the form of joint watermarking and compression (JWC). Moreover, the other requirement is that watermarking process should not increase bit rate for the compressed data to a large extent while satisfying high value of document-to-watermark ratio (DWR) and watermark decoding reliability. Over and above, it is desirable that watermarking algorithm must be compatible with ease of integration with the existing compression framework, for example, JPEG and JPEG 2000 compression for digital images.