earticle

영어

The central idea of this paper is to propose an innovative watermarking scheme for digital image authentication which embeds watermark into the host image and provides qualities such as imperceptibility, robustness and security. A watermark signal is constructed from feature of original image instead of using external watermark. Several pixels are randomly selected from original image, so that all of them have a valid 3x3 neighborhoods. A binary sequence is constructed from those pixels by comparing them against average values of neighborhoods. The binary sequence is then converted into a watermark pattern in the form of a Hankel matrix to improve security of watermarking process and is then embedded within the host image. The operation of embedding and extraction of watermark is done in high frequency domain of Discrete Wavelet Transform since small modifications in this domain are not perceived by human eyes. This watermarking scheme deals with the extraction of the watermark information in the absence of original image, hence the blind scheme was obtained. The proposed algorithm was verified under common image processing attacks such as salt & pepper noise, Gaussian noise, median filtering, linear filtering, JPEG compression, blurring, scaling, intensity adjustment and histogram equalization. Peak Signal to Noise Ratio (PSNR) and Similarity Ratio (SR) are computed to measure imperceptibility and robustness of the watermark respectively.