关键词: 半脆弱图像水印, 水印认证, Sobel边缘检测, Zernike不变矩, 离散小波变换（DWT）, 权重欧式距离

Abstract: In order to make the image watermarking algorithm have authentication function, this paper proposes a semi-fragile image watermarking authentication algorithm based on Sobel edge detection and Zernike invariant moments. The normalized carrier image is third-level decomposed based on discrete wavelet transform (DWT) to get 10 sub-bands LL₃,HL₃,LH₃,HH₃,HH₂,HL₂,LH₂,HL₁,LH₁,HH₁. Then the sub-band LL₃ is processed by using the Sobel operator and Zernike moments. And the watermark embedding mechanism is designed to embed the watermark information into DWT coefficients of sub-band LL₃ for forming the initial watermark image. And the Sobel operator is used again to detect the initial watermark image for obtaining the edge map to determine the embedded position, so that the final watermark image is got by embedding the watermark information into Zernike moment of edge map. Meanwhile, the watermark restoration method is established to extract the complete watermark information. Finally, the watermark authentication method is designed based on weighted Euclidean distance to determine the authenticity of the watermark information. The experimental results show that this algorithm has higher robust and lower tamper rate.

Key words: semi-fragile image watermarking, watermark authentication, Sobel edge detection, Zernike invariant moments, disceret wavelet transform (DWT), weighted Euclidean distance