A robust image watermarking algorithm based on non-uniform rectangular partition and encryption scrambling

The watermark is more likely to prevent itself from JPEG-compression attack when it is embedded into the DC values of 8×8 DCT blocks. However, embedding the watermark with the same intensity into the DC values of DCT blocks may distort the watermarked image to a large extent. To solve this problem, a novel robust image-watermark algorithm is proposed with the characteristics of selective embedding intensity based on the non-uniform partition. Firstly, following the rectangular partition algorithm, the image has automatically been partitioned into different rectangles which reflect the grey-distribution characteristics in different dimensions. Secondly, the suitable embedded intensities have been chosen, according the number of rectangles within each 8×8 block. Meanwhile, in order to increase the anti-cropping function and the security of the algorithm, MUST* Encryption Algorithm is applied to encrypt the pixel-locations of the watermark before the watermark is embedded. The results of the experiments have showed that this algorithm is robust against noising attack, cropping attack, especially the JPEG-compression attack and no obvious distortion appeared in the watermarked image.