Adaptive watermarking in Hadamard transform coefficients of textured image blocks

Due to increasing of concerns amongst digital content owners, many watermarking methods have been proposed in recent years to protect copyright of digital images. These methods are classified as either spatial or frequency domain techniques. Since fidelity and robustness are important factors in watermarking, many methods have been proposed that try to increase robustness as well as preserving the fidelity. In this paper a Hadamard based watermarking algorithm is proposed that embeds a binary logo into Hadamard coefficient of image blocks. To preserve fidelity of watermarked image, proper blocks are chosen according to their entropy. Furthermore a compression method is used to decrease length of watermark in order to embed larger logo in the cover image. The experimental results and comparison to another Hadamard based method shows that proposed algorithm has increased robustness against some of image processing attacks such as JPEG compression, resizing and median filtering. Furthermore it has preserved the fidelity of watermarked image very well.