A comprehensive review on optimization-based image watermarking techniques for copyright protection

Due to exponential growth of digital world the online data is also drastically increasing. This multimedia data may contain text, video, audio, and images. After the Covid-19 pandemic era, the volume of digital images is also increasing drastically. There is a need to secure these images during the transmission. One of the best methods to protect this vital information is watermarking. Image watermarking is a technique in which a watermark is embed into the cover to secure the copyright and verify the identity. During the watermarking process, there are some characteristics like robustness, imperceptibility, capacity, security, and authentication must be balance. To make a balance among these properties, optimization techniques play a vital role. During the watermark embedding there is a scaling factor which must be optimized to get optimum value. This scaling factor balances the properties of the watermarking scheme. Different optimization techniques such as particle swarm, brainstorm, lightning search etc. can be used to get optimal scaling factor. Based on the literature review presented several research gaps are formulated in this article which clearly signifies for the necessity of the metaheuristic approaches. Open research challenges related to optimization techniques are elaborated for the researchers that can be explored in future.