A Blind Image Watermarking Scheme Utilizing BTC Bitplanes

Abstract

This paper presents a novel image watermarking scheme utilizing Block Truncation Coding (BTC). This scheme uses BTC to guide the watermark embedding and extraction processes. During the embedding process, the original cover image is first partitioned into non-overlapping 4×4 blocks. Then, BTC is performed on each block to obtain its BTC bitplane, and the number of ‘1’s in the bitplane is counted. If the watermark bit to be embedded is ‘1’ and the number of ‘1’s is odd, or the watermark bit to be embedded is ‘0’ and the number of ‘1’s is even, then no change is made. Otherwise, by changing at most three pixels in the original image block, the number of ‘1’s (or ‘0’s) in the renewed bitplane are forced to be odd for the watermark bit ‘1’ or to be even for the watermark bit ‘0’. During the extraction process, BTC is first performed on each block to obtain its bitplane. If the number of ‘1’s in the bitplane is odd, then the embedded watermark bit is ‘1’. Otherwise, the embedded watermark bit is ‘0’. The experimental results show that the proposed watermarking method is semi-fragile except for the changes in brightness and contrast; therefore, the proposed method can be used for image authentication.