Evaluating Digital Image Watermarking based on Image Interlacing , DWT & DCT .

Digital watermarking is important as it facilitates security & protection to digital data whereas when this data are used within international network they must exist in compressed format as it requires minimum transmission bandwidth & reduced storage requirement. Hence our proposed scheme will serve as a solution for maintaining the digital data in compressed state. To achieve this goal the procedure will perform watermarking of interlaced image based on DWT – DCT algorithm. In order to embed the watermark we transform the image into subimages using 2level interlacing, then the selected subimage is 1level decomposed using DWT haar wavelet transform, from the decomposition the sub-image is selected which is also transform by DCT algorithm. Hence the watermarked image is formed by inverse transform of DCT followed by IDWT. Finally, the secret message is extracted by dithering the watermarked image using DWT followed by DCT algorithm. Using this technique the ownership can be authenticated with the image of size more than 50% less than the original. The experimental result shows that the proposed algorithm imparts good imperceptibility but when robustness is considered it works better under the situation when the watermarked image is not exposed to any attack and if the watermarked image is exposed to attacks the watermark bits gets highly manipulated which results in loss of secret message. Keywords— Digital watermarking, image interlacing, DWT, DCT.