A statistical property based image watermarking using permutation and CT-QR

A novel digital image watermarking scheme based on Contourlet Transform (CT) and QR factorization method is proposed in this paper. Contourlet Transform is applied to the original and watermark image so that it decomposes into subbands. The lowest frequency coefficients are divided into blocks. The standard deviation (SD) of each block is calculated and the blocks that have SD greater than a predefined threshold are decomposed by QR based factorization method. The watermark is permuted after the application of CT. After the embedding process the blocks are joined again to obtain the watermarked image. It has been shown experimentally that even after application of attacks on the watermarked image, the watermark can be efficiently extracted from at least one block of lowest frequency subband. The preprocessing of the watermark and division into blocks has made the scheme more robust to image processing attacks such as Scaling, Cropping, Rotation, Gaussian noise and Compression.