## 1 Introduction  
Online piracy has caused significant financial losses and job displacement in some countries, amounting to over USD 12 billion annually and 70,000 lost jobs according to the Recording Industry Association of America (RIAA) [1]. The increased use of the internet positively correlates with rising privacy concerns for digital media usage. To alleviate the effects of pirating of such media, digital watermarking is one solution. Digital watermarking is a form of data-hiding technology [2] that involves masking pre-designed information into digital media such as images, videos, or audio. There are various types of digital watermarking schemes, including those based on spatial and frequency domains, and they are classified as robust, semi-fragile, and fragile methods [3]. Of course, a given technique has its own advantages and disadvantages. However, the use of a specific method depends on the application itself. The internet's widespread use has made it quick and effortless to distribute digital media such as audio, video, and images. However, this convenience has also resulted in critical issues involving copyright infringement and authentication. Watermarking is one of the most effective and widely used techniques to address these concerns. Typically, image watermarking techniques follow a general set of steps that include a watermark embedder and a watermark detector, as depicted in Figure 1.  
Watermarking systems need to have specific properties tailored to their intended applications, and as such there is no standard set of properties that all watermarking systems must meet. However, one of the most critical requirements is imperceptibility [4]. Image watermarking involves embedding secret data into a host image without degrading the quality of the watermarked image (imperceptibility). Imperceptibility requires that the quality of the original image is preserved even after inserting the watermark, such that it remains invisible to human eyes [5]. A watermarking approach is considered imperceptible if the host and watermarked images are visually indistinguishable. A robust watermarking scheme should not introduce artifacts into the images, and to assess imperceptibility, objective methods such as the peak signal-to-noise ratio (PSNR) are commonly used [6; 7]. In addition to immanence, the watermarking method must also meet robustness requirements. A robust watermark is one that can largely survive variations in the host image (maintaining content with a level of computer independence) whilst other non-domain attack vectors are in play, i.e., cropping, resizing (scaling), contrast adjustment, and JPEG compression [4]. Balancing these numbers to find the watermark's secret formula, one that is strong enough but which does not cause severe degradation of the image, can be difficult. Thus, we should evaluate watermarking algorithms that are good enough to resist attacks with caution, and also aim to prevent significant changes in the quality of the embedded image. The methods of watermarking that are best suited for proof of copyright and ownership in digital images are robust watermarking techniques. These are intended to withstand several image processing attacks that would either tamper with or erase the watermark. Therefore, robust watermarking techniques are employed to support intellectual property rights, including but not limited to digital image copyright, content authentication, and ownership proof [3]. Sensitive watermark-enabled methods are useful when one requires copyright protection, whilst fragile watermarking methods provide image authentication to confirm the integrity of an image without manipulation or modification. Semi-fragile watermarking is effective and strong, but it is also sensitive to higher image processing operations, and it can be employed for several tamper-detecting schemes [3]. Figure 1: The architecture of a digital image watermarking system.