Research On Digital Watermarking Algorithm For Images Based On Discrete Wavelet Transformation

The basic idea of digital watermarking is embedding the copyright information into thedigital product by some special way, in order to hit the target such as copyright protection.The watermarking technology becomes a hot topic in the information hiding, and has paidextensively attention by scholars.By using the advantage of the wavelet transformation in image processing, and based onthe stability of differences with wavelet coefficients of the image, we proposes awatermarking algorithm. Our main research works are summarized as follows:(1) Firstly, we do the statistical analysis for the sub-bands that derived by three-levelwavelet decomposition, then the select sub-bands LH3and HL3to embed the watermarking.Simultaneously, we analyze several quantization algorithms about SDQ, and present a betterquantization one.(2) For the sub-bands LH3and HL3, let the four coefficients of the same parentcoefficients consist of a data block, in the light of secret key, this way can improve thesecurity of watermarking system.(3) For each data set which contains two data blocks, we find out the most importantwavelet coefficients of two corresponding data block and calculation of their amplitudedifference. Amplitude difference depicts the difference between data sets. We select the datasets with larger and smaller distinguish difference as the ones embedding watermarking.(4) When we quantize and revise those coefficients, according to the different degree ofdifference, we apply the different quantization methods, such that the less the coefficients arequantized and revised, the smaller the amplitudes are revised.(5) Let the stability of differences with wavelet coefficients as the stable property of theimage, furthermore, we propose a Zero watermarking algorithm based on DWT.