Owing to personal computers being applied in many fields and Internet
becoming popular and easier to use, most information is transmitted with digital
format. Therefore, data copying and back up are more and more easier in the world
wide web and multimedia. The copyright and authentication gradually lose their
security. How to protect intellectual property becomes important in technical study
and research. Recently, the watermarking technique was proposed to solve the
problem of protecting the intellectual property.
In this paper, a watermark embedded in the host image by DCT transform has
been proposed. There are several papers using the same manner to embed watermark
into middle-band coefficients of DCT block. The Joint Photograph Expert Group
(JPEG) image compression usually discards the high-band frequency in DCT block
including some middle-band data. In this paper the lower-band coefficient of DCT
block was employed, since it is robust against the attack by the JPEG. In order to
improve the imperceptions, only one bit was embedded in each coefficient of a DCT
block. The experimental results show the proposed approach is correct.
