Robust watermarking scheme based on the JPEG2000 standard

We perform an empirical evaluation of the lossy compression properties of the JPEG2000 standard for watermarking and fingerprinting purposes. The JPEG2000 standard is used as a basic tool for determining both how and where the embedded watermark should be placed in the image. The original image is slightly modified to generate a similar image (but indistinguishable by the observer), and the mark is embedded in the pixels presenting differences between both images. The reconstruction process uses the original and the modified images to detect the embedded mark in any possible attacked image, so the watermarking scheme is non-blind. Previous experiments show that the properties of the resulting watermarking scheme depend strongly on the transformation stage characteristics of the lossy image compression system. Several parameters related to the JPEG2000 standard are tested, in addition to the compression ratio determined by the desired bit rate: the wavelet transform, block size, and the number of levels of decomposition for each block. These parameters affect not only the capacity but also the robustness of the watermarking scheme, which depends on the number of differing pixels between the original image and the slightly modified one, and the distribution of such differences. For evaluation purposes, we use the Stirmark benchmark and the classical image corpus set for lossy image compression. We compare the impact on system performance of each of the JPEG2000 standard parameters for several kinds of attacks, namely, filtering (including sharpening); JPEG lossy compression; cropping; row and column removal; and a combination of rotation, cropping, and scaling. The false positive rate is also studied. Results show that the proposed watermarking scheme based on the JPEG2000 standard is robust against most of the classical image manipulation operation, and therefore, is suitable for watermarking purposes. Furthermore, the proposed watermarking scheme can be also upgraded to be used as a fingerprinting scheme once the embedded mark is properly coded, due to the use of a collusion scheme.