Comparison between the cosine and hartley based naturalness preserving transforms for image watermarking and data hiding

A comparison between two image-watermarking schemes is demonstrated in this paper. The proposed watermarking techniques use modified forms of the naturalness preserving transform (NPT) to encode a watermark logo image into a host image. The modified NPT forms employ the Hartley and cosine matrices, respectively, instead of the Hadamard matrix used in the classical Hadamard based NPT. The modified NPT enhances the quality of the transformed image by reducing the artifacts that occur in images transformed via the Hadamard NPT. The proposed watermark has proven robust against variety of image attacks including, image filtering, JPEG compression, cropping, and noise.