Data Hiding in Symmetric Circular String Art

Abstract

Creative digital artwork is usually the outcome of a long period of intellectual creation and labor of an artist. Similarly, computer-created digital artwork is an outcome of a large amount of machine time and computational resources. However, such intellectual properties can be easily copied by illegal users. Copyright protection of digital art is increasingly more important than before. Recently, using a computational approach to generate string art tends to be popular and attractive. To protect the illegal usage of the digital form of string art, we propose a data hiding algorithm specifically designed for string art. A digital string art image consists of a sequence of string lines, each specified by two nails fixed at the two ends of that line. The encrypted secret data (the watermark) is embedded into the list of line segments by odd–even modulation, where a bit ‘1’ is embedded by forcing the next node to be an odd node, and a bit ‘0’ is embedded by forcing the next node to be an even node. To minimize the impact of data embedding on the quality of the original string art image, a local optimization algorithm is developed to select the nodes that produce minimal distortion. To quantify the embedding distortion, we introduce a smoothing filter model for the human vision system (HVS) specifically tailored to string art image. Experimental results show that using the proposed algorithm, the distortion between the original string art image and the watermarked string art image is unnoticeable. The modified string art image is statistically indistinguishable from the original string art, and hence is secure under steganalysis. To our best knowledge, this is the first work towards data hiding and copyright protection of digital string art.