A variable block-size dot-based watermarking method

We propose a digital watermarking method for still images in the discrete cosine transform (DCT) domain. The adaptive watermark insertion method is employed to increase the invisibility of the inserted watermark in images, in which variable block-size is adopted depending on the characteristics of the region. Experimental results with several test images show that the proposed watermarking method is robust to several common image processing techniques, including Joint Photographic Experts Group (JPEG) compression, lowpass filtering, multiple watermarking, and cropping.