In this paper

an algorithm which automatically transforms number to gray-image using the number as key is proposed

distinct number leading to distinct gray-image.Its implementation is that random sequence is made by chaotic iterations using number as seed

then the sequence is transformed to two-value image.By cellular automata processing and after smoothing operation the gray-image is generated.The gray-image is regarded as a digital watermarking pattern and the pattern has most of its power concentrated in low frequencies.The watermarking is embbed into original image in spatial apace

and it is detected by using DCT.The experiment results show that the pattern has good property.The watermarking algorithm based on the pattern can resist some usual attacks.