Digital Image Watermarking using Discrete Wavelet Transform and Arithmetic Progression technique

Nowadays it has become very easy to use digital information present over the internet because of the fast development in Information Technology sector. Digital Watermarking makes an attempt to resolve the problems associated with the management of property of media. It ends up in unauthorized copying and redistribution of digital content. In the proposed method, cover image is decomposed into low and high frequency components by the application of 1-level Discrete Wavelet Transform. Average of each subband is calculated. The watermark is embedded into the 1-level high-high, high-low, low-high subband of cover image using Arithmetic Progression technique. The subband which has the smallest average is to be embedded first. After that, the watermarked image is projected to several attacks like median filtering, JPEG compression, Gaussian low-pass filtering, shearing, cropping, rotation etc. with different distortion strengths. The watermark which is embedded in the middle frequency subbands and high frequency subband is taken out by similar mechanism. The imperceptibility and robustness of the watermarked image is checked out by measuring the Peak Signal to Noise Ratio (PSNR) and Structural Similarity Index values. From the implementation results, we came to know that this watermarking algorithm can withstand many image manipulations compared to other existing DWT based methods.