Robust image watermarking scheme using bit-plane of hadamard coefficients

Nowadays, due to widespread usage of the Internet, digital contents are distributed quickly and inexpensively throughout the world. Watermarking techniques can help protect authenticity of digital contents by identifying their owners. In a watermarking procedure, owner information may be embedded in the spatial domain or transform domain of host images. Since watermarking algorithms must be tamper resistant and transparent, we present a watermarking method based on a transform domain. In this method, we employ Hadamard transform as it requires simpler operations compared to other transforms such as discrete cosine transform (DCT) and discrete wavelet transform (DWT) while it still attains robustness. We analyze each bit of the Hadamard's coefficients in terms of robustness and transparency for hiding the watermark information and find a bit-plane that maintains both robustness and transparency. After that, watermark information is hidden redundantly in the selected bit-plane. The proposed extraction algorithm is classified as a blind algorithm since it extracts all versions of the concealed watermark with no information from the host image. The output of the extraction algorithm is a logo obtained by an intelligent voting among all versions of the hidden logo. The experimental results show that the proposed method, while providing transparency, is robust against many image processing attacks such as compression, image cropping and Gaussian filtering.