Abstract: This article researches on the algorithm of embedding digital watermarking in static gray images based on discrete cosine transformation (DCT), and focuses on the ways and means of embedding watermarking. The algorithmic principle is dividing the watermarking and original images into blocks, converting the blocks to DCT domain, and embedding them correspondently. However, the watermarking must be embedded in a certain place, that is embedding the watermarking to images in some of the intermediate frequency near low frequency part. The purpose is to make the embedded watermarking better hidden and resistant to attack. Experimental results show that under certain conditions, the watermarking can be well hidden in the original image with a certain degree of resistance to attack of smear or shear.

Key words: gray image, digital watermarking, discrete cosine transformation