ROBUST DIGITAL IMAGE WATERMARKING BY USING DCT TECHNIQUE

Nowadays the internet and the personal computers becomes more popular because these are very easy to handle and use and being used in many fields for the transmission of most of the information in digital format. Due to the digital format transmission the copy write protection for this data is necessary in the World Wide Web and multimedia applications. The copyright protection and authentication generally loses their security of the data. Therefore it is necessary to protect the intellectual property in technical study and the research. Recently, most of the watermarking techniques are used to protect the intellectual property of the data. In this paper, an effective algorithm is present to embed the watermark into the host image by using DCT transform. There were many papers presented by using the same concept to embed watermark into the middle band coefficients of DCT blocks. But these papers have disadvantage that these are not computable for the Joint Photograph Expert Group (JPEG) image compression. The JPEG compression generally discards the high band frequencies in the DCT block it also includes some middle band data. In this paper the lower band coefficients of DCT blocks was employed, because it is robust against the attacks by the JPEG. In order to improve the imperceptions, only one bit was embedded in each coefficient of a DCT block. Finally, the experimental results show the proposed algorithm suitable for different image compression techniques like as JPEG, BMP, TIFF, GIF and PNG, etc