A blind color image watermarking algorithm based on Hadamard transform and TLBO algorithm

Abstract

For the sake of better protect the copyright of color images, an efficient color image watermarking algorithm based on Hadamard transform and teaching-learning-based optimization (TLBO) algorithm is proposed in this paper. In the stage of embedding watermark, different watermark embedding strategies are employed in 4 × 4 blocks based on the impact level of pixel caused by the high and low bit of watermark and taking into account the energy concentration characteristics of the Hadamard matrix. To enhance the robustness of the watermarking algorithm, the voting system is designed for the high-four bits of watermark information. Simultaneously, the permutation ordered binary (POB) number system is used to compress the low-four bits of watermark information for improving the invisibility of the watermarked image and the embedding capacity. When the watermark needs to be extracted, the inverse process of POB number system transform is optimized, and the time of watermark extraction is shortened. Finally, the TLBO algorithm is used to optimize the watermarking algorithm parameters for saving the experimental time while considering both invisibility and robustness of the algorithm. In comparison to the other algorithms examined in this research, the experimental results demonstrate that the proposed watermarking algorithm exhibits several performance enhancements, these include aspects such as robustness, running time, watermark embedding capacity, security and invisibility.