An Improved Watermarking Detect Algorithm for Color Image in Spatial Domain

This paper presents an improved watermarking detected algorithm for color image based on a block probability in spatial domain. A binary watermark image is permutated using sequence numbers generated by a secret key and Gray code, and then embedded four times in different positions by a secret key. Each bit of the binary encoded watermark is embedded by modifying the intensities of a non-overlapping block of 8*8 of the blue component of the host image. In watermarking extract scheme, the scale invariant features of images are extracted, and the match points between the watermarking image and the reference image are found. Then the watermarking image is corrected by affine transform of these match points. The improved extraction method of the watermark is by comparing the intensities of a block of 8*8 of all components of the watermarked and the original images and calculating the probability of detecting binary watermark. Tested by benchmark Stirmark 4.0, the experimental results show that the algorithm is robust against various kinds of attacks such as Affine, Rotating, Cropping, Scaling, JPEG compression, Mean filtering and so on.