Digital Image Watermarking Based on Embedded Wavelet Coding
基于嵌入式小波编码的数字图像水印算法

Watermarking is one of the current copyright protection methods that have recently received considerable attention. In this paper, we introduce a wavelet transform based watermark casting scheme for digital images. The proposed method searches the significant coefficients across subbands to embed the watermarks into the significant wavelet coefficients. The watermark is adaptively weighted in different subbands according to the recommended mask values of wavelet coefficients by Watson. The current quantization threshold for each subband is also used as the weighting function of the embedded watermark. The fidelity of the watermarked image can be adjusted by using a weighting factor of the cast watermark. The casting and detecting of watermarks is hierarchical. In the case when the received image is not distorted significantly, the calculation of cross correlations with the whole size of the image may not be necessary, therefore much of the computational load can be saved. Experimental results show that the DWT based watermark approach can provide an excellent protection under various attacks.