Wavelet Base Secure Spread Spectrum Image Watermarking

• Main Authors: Hsiao-Cheng Hsu, 許孝成
• Other Authors: Y. C. Ouyang
• Format: Others
• Language: zh-TW
• Published: 2003
• Online Access: http://ndltd.ncl.edu.tw/handle/45502910987963543672

碩士 === 國立中興大學 === 電機工程學系 === 91 === The digital watermarks should be hided and invisible by the human visual system. The spread spectrum techniques are used to achieve the goal. The original image is transformed form spatial domain to frequency domain by using discrete wavelet transform (DWT). We insert the spread spectrum PN-code and use modulo-2 operator to secure the watermark. The watermark is embedded into the LL3 sub-band after 3 times DWT. A multilevel detection is proposed to effectively watermark which can increase the retrieval performance. Form the experimental result, the proposed method is robust even under heavy attacks. For example, big compression ratio for JPEG and JPEG 2000, the retrieval watermarks still survive.