Development of Digital Image Watermarking Technology on the Wavelet Domain

• Main Authors: Lin, Chiu-Chun, 林秋君
• Other Authors: Chen, Der-Fa
• Format: Others
• Language: en_US
• Published: 2017
• Online Access: http://ndltd.ncl.edu.tw/handle/4yb287

博士 === 國立彰化師範大學 === 工業教育與技術學系 === 105 === Abstract This study presents two image watermarking schemes. The first scheme embeds the watermark using the optimal modulo 2 quantization in DWT coefficients of the associated image. The DWT multi-coefficients are adjusted according to an optimization formula which maximizes the objective function, i.e., the peak signal-to-noise ratio (PSNR) of the watermarked image. The second scheme embeds the watermark using the optimal SVD quantization in DWT coefficients of the associated image. The purpose of this scheme is to improve the robustness of traditional SVD-based image watermarking scheme. The singular values of LH3 and HL3 parts of the image’s DWT decomposition are computed and multiple singular values are grouped as a block and quantized to embed the watermarks. During this process an optimization technique is applied to minimize the difference between original and watermarked singular values. In order to implement these two watermarking schemes in optimal sense, the PSNR is considered as a performance index in the matrix form. And then the functional that relates the performance index to the quantization technique is obtained. The Lagrange Principle is utilized to calculate the optimal solution based on this functional which is then applied to embed the watermark. Experimental results show that these two watermark schemes can keep high PSNR and also achieve a better BER even though the bit number of the embedded watermark increases.