A robust DWT-based image watermarking algorithm

In general, visually recognizable watermarks offer to the owner of digital material a stronger impact than the pseudo random sequence watermarks at the copyright claiming time. However due to a larger amount of the watermark information, the watermark transparency and robustness requirements cannot be easily simultaneously satisfied. This paper proposes a robust watermarking algorithm based on the Discrete Wavelet Transform (DWT), in which owner of the digital material must keep only the original unmarked image and a secrete key. The watermark patterns in the proposed algorithm can be binary or gray scale images whose size is not limited by the size of the image to be protected. Experimental results show the watermark transparency of the proposed algorithm even if the binary or gray scale watermark pattern is four times bigger than the image to be protected. The robustness of embedded watermark pattern to common attacks such as JPEG compression, noise contamination, illumination and contrast modification are also shown.