Digital Image Watermarking by Using Discrete Wavelet Transform and Discrete Cosine Transform and Comparison Based on PSNR

Digital watermarking is a technique which allows an individual to add hidden copyright notices or other verification messages to digital audio, video, or image signals and documents. Watermarking can be done by using least significant bit (LSB), singular value decomposition (SVD), Discrete Fourier Transform (DFT), Discrete cosine transform (DCT) and Discrete wavelet transform (DWT) techniques. In this paper Discrete cosine transform (DCT) and Discrete wavelet transform (DWT) are used for embedding and extraction of watermark. DWT and DCT are compared with respect to peak signal to noise ratio (PSNR) at a different threshold values. DWT gives better Image quality then DCT.