The Research of Watermarking Technique for Color images

• Main Authors: Chiang, Chung-Shi, 江中熈
• Other Authors: Ping S. Huang
• Format: Others
• Language: zh-TW
• Published: 2005
• Online Access: http://ndltd.ncl.edu.tw/handle/90354344870681876143

博士 === 國防大學中正理工學院 === 國防科學研究所 === 94 === Most color watermarking methods are realized by modifying the image luminance or by processing each component of color space separately. This thesis presents two novel and robust color image watermarking approaches for applications in copyright protection and digital archives. By adopting the characteristics of color information, we have developed the approach of saturation adjustment under frequency domains (i.e. DCT, DWT) for hiding grayscale logos into the saturation component of color images. Firstly, we study the definition of DC component in the DCT domain, and present an approach for hiding the watermark into DC components of the color image directly in spatial domain. The merit of proposed approach provides not only promising watermarking performance but also computational efficiency. Experimental results demonstrate that this scheme can successfully make the watermark robust to image operation attacks. Then, the second embedding procedures are performed in the DWT domains and the lower frequency areas are selected to embed the watermarks. To improve the watermark detection robustness, we propose an adaptive weighting scheme to fuse the extracted watermarks in the extraction stage. Experimental results show that the proposed approach can effectively help the watermark perceptually invisible and robust to image processing operations such as StirMark and PhotoImpact attacks. Instead of hiding the watermark into the intensity, the saturation adjustment approach redirects the watermark to the saturation with superior invisibility. Since this scheme is a non-blind technique, we plan to investigate the relationship of color components and develop a blind watermarking technique in the future.