Today, technology is at a tremendous pace, the software and hardware prices are acceptable, and the popularization of Internet, the color images can be obtained easily. It is a difficult problem for affirming copyrights, and digital watermark is a well known technology to judge the copyright dispute. But the most watermark technology embed the binary watermark in gray-scale image, in the multimedia world, such solution is insufficient. This thesis proposes a method can use less calculation to embed the color watermark in color image, and does not need the original image to extract the embedded color watermark. First, this study counts the most 24 colors of color watermark that we want to embed, and use these colors as the representative of color watermark. Then uses a pseudo random number generator to scramble the represented color watermark, and saves the random seed as the secret key. This proposed method embeds the color watermark in B-channel of the RGB color space. We can utilize adjoin pixel relation of similar gray-scale level, with the different permutation order according to pixel values of 2x2 block, to represent 24 kinds of different color, and can emphasize the distance among pixels with a parameter d to increase the robustness of the watermark. While extracting the embedded watermark, only need scan the permutation order of 2x2 block for the disputant image, and need not compare the original image. The experiment results prove the method proposed by this thesis is finer than methods have been proposed in the literatures.
