A Unified Compression and Watermarking Scheme for MT-BTC Images

Abstract

As most multimedia is compressed for optimal storage or transmission, the watermarking during compression is more appropriate and demanding. Multi-tone block truncation coding image (MT-BTC) is a latest and superior version of halftone based block truncation coding images. In this paper, a novel watermarking strategy is proposed for MT-BTC images using the adaptive dither array selection (ADAS) and inter-tone shifting. ADAS method utilize dither array constructed using two different gaussian filters based on the Human Visual System (HVS) model to embed the watermark information. Further, various configuration of dither array such as actual, conjugate, transpose and transpose conjugate is used to embed more data. Moreover, a new approach termed inter-tone shifting is also proposed to improve the decoding rate and security. The decoding scheme is performed using the pattern similarity on the dithered watermarked image. For result validation, a 2,4,6 and 8-Tone watermark image is embedded in the 4-Tone MTBTC image. From extensive analysis on decoding rate and robustness, it has been validated that the proposed scheme outperforms many halftone watermarking and consistent with conventional BTC methods.