Punched Image Watermarking: A Novel Fast Fractal Coding Based Technique

Fractal image coding has proved its efficiency as a compression technique for digital images. Recently, using fractal coding for digital image watermarking has gained considerable attention. In this paper, a novel fast image watermarking and data hiding technique is proposed. Watermark embedding is accomplished during region based fractal encoding process which confines the domain pool search space to a certain region according to the mean of the range block. Different domain blocks´ regions are assigned to represent either 0 or 1. Depending on the value of the bit to be hidden, the search space is limited to the region assigned to it. In case of hiding in a range block that belongs to a region that does not represent the bit to be hidden in it, bit padding technique is used at the encoder while punching is used at the decoder. Furthermore, at the decoder extracting the watermark needs only checking the mean of the hiding range blocks rather than re-encoding the whole image which significantly enhances the time needed for watermark extraction. The proposed technique is robust against common noise signals such as additive white Gaussian noise AWGN and salt & pepper noise.