Dwt-based Color Image Watermarking Algorithm

Digital image watermark, as a branch of data hiding technology, imbeds symbol information into the protected image using the redundancy attribute of Human Visual System. As an effective approach of copyright of digital image, it has become a hotspot in the field of information security recently.In this paper ,three watermark embedding algorithm based on DWT is improved. The first algorithm inserts the watermarks based on DWT The scheme that embeds image data invisibly into a colorimage was proposed based on human visual model.. the original color image is transformed into RGB color space, and the watermark was embedded in Y component then each LL[3] coefficient of RGB elements is added by scaled gray levels elements of watermarks . then we take the IDWT of the modified DWT coefficients and unchanged coefficients to form color watermarked image. The second algorithm is based on permuted image and SVD, we embedded gray watermark in colour image's dwt components. in order to make this algorithm is of better invisibility and very robust , The given color image is split into its three components RGB and a watermark was embedded into blue component of color image. It was found by experiment that the perceptive quality of original image might be better kept when watermark was embedded into blue component than into other color components. A Threshold value was setted , if the diagonal of value based on SVD was less than the threshold valve, we can substitute the value of before for the value of the diagonal . The third algorithm is about the YIQ color space is adopted to embed the watermark in the paper.