Watermarking and Authentication of Color Images Based on Segmentation of the xyZ Color Space

In this paper we propose a new strategy of watermarking which extends the principle of histogram specification to color histogram. The proposed scheme embeds into a color image a color watermark from either the xy chromatic plane or the xyY color space. The scheme resists to geometric attacks (e.g., rotation, scaling, etc.,) and, within some limits, to JPEG compression. The scheme uses a secret binary pattern, or combines some patterns generated by a secret key to modify the chromatic distribution of an image. By using the inverse pattern, the watermark is detected without knowing the original image. Examples of images and attacks are given to illustrate the relevance of. the proposed approach, i.e., its invisibility and the robustness. In the second part of this paper we investigate the usefulness of our watermarking approach for color image authentication. Several experiments are presented to show that our scheme ensures image authentication, detects tampered regions in case of malicious attacks and ensures a certain degree of robustness to common image manipulations like JPEG compression, etc. Compared with other blind authentication schemes, the experiments show that the detection ability the invisibility, as well as the robustness to some common image processing are improved.