A Blind Watermarking Using Data Matrix and Changing Coefficients in Wavelet Domain

摘要

In this paper, we propose a blind watermarking using the Discrete Wavelet Transform (DWT) technique. We have shown a robustness in several attacks by inserting the watermark in the frequency domain instead of spatial domain in the image. Also, we can extract watermark without the original image using this blind watermarking. An original image is transformed into the 4 sub-band areas (HH, HL, LH, LL) by the DWT. We select the two sub-band areas (HL, LH) for watermarking, except for the low-low (LL, HH) sub-band area. For watermarking, a watermark is encrypted by an encryption key, and it holds a certain value of two sub-bands, which is selected according to the value of watermark that we want to insert or change. And we insert watermark to the image. For extraction, a watermarked image is transformed by DWT, we compare the coefficient values of two sub-bands used in inserting watermarking, we extract the encrypted watermark, and we reconstruct the watermark by the encryption key. We apply the proposed method to the data matrix that is a two-dimension bar-code. For error detection code and error correction code, we use the ECC 200. For the JPEG image with the watermark, we could get the better PSNR(Peak Signal to Noise Ratio) and NC(Normalized Correlation) for the performance evaluation.