Blind digital image watermarking using adpative casting energy in different resolutions of wavelet transform

With ubiquitous computing, safeguarding the creative content and intellectual property in a digital form have become essential necessity. Watermarking is one such technique for protecting the digital data like image, video and audio signal. In this paper, digital image watermarking technique is proposed for protecting the digital images based on discrete wavelet transform due its excellent spatial localization, frequency spread and multi-resolution analysis similar to human visual system. The method involves a visual watermark (grayscale image) which is transformed using discrete cosine transform for getting low frequency coefficients in frequency domain. The low frequency coefficients of transformed watermark image contain maximum visual data information. Then, the original image is transformed using the discrete wavelet transform and watermark is embedded by modifying the coefficients of LL bands with appropriate imperceptibility and robustness. The multi-energy watermarking technique using the qualified significant wavelet tree (QSWT) are used to select the locations for embedding and extracting image watermark. QSWT provides robustness by allowing adaptive casting energy in different resolutions available from the wavelet transform. The performance of this scheme is robust to sharpening, smoothening, JPEG compression and image cropping.