Semi-fragile watermarking for text document images authentication

The proposed novel semi-fragile watermarking method makes use of prioritized noise suppression patterns; it takes into account the smoothness and connectivity in a 5×5 neighborhood. This is particularly necessary when the original text document image is noisy. The content signature watermark is generated by uniquely mapping the binary bit pattern in each block to a binary bit. A novel way of embedding the content signature watermark in each block is proposed which is effective in detecting malicious attacks. Shuffling is applied to the host image to increase the security of the algorithm. A minimum flipping distance is imposed to control the visual quality. Experimental results validate the arguments made.