## 2 Related Literature and Problem Statement
### Literature Review
Experiments found PSNR > 38 dB, which means a better imperceptibility of the watermarked image. The method is robust against WF, MF, low-pass Gaussian filter (LPGF), AF, GN, SN, SPN, JPEG compression, JPEG 2000, rescaling, HE, sharpening, and motion blur attacks. Also, the FPD problem can be solved by this method. But, hybrid attacks and watermark embedding capacity are not observed. Also, they do not use any security technique for ensuring watermark image security. In scheme [PERSON] et al., 2020 (2016), another blind method is proposed based on fan beam transform (FBT) and QR decomposition. At first, FBT is applied to the color host image, and QR decomposition is applied to it. The watermark is inserted into the selected coefficients of the host image. The method results in high imperceptibility, as PSNR > 54 dB. The method is robust against JPEG compression, rotation, SPN, GN, SN, Poisson noise (PN), contrast adjustment, sharpening, WF, and MF attacks. But, the method is less robust against cropping attacks. Also, hybrid attacks, copy attacks, security issues, and embedding capacity are not examined. In 2021, [PERSON] et al. (2013) proposed a hybrid method based on discrete cosine transform (DCT), DWT, and SVD. At first, the watermark image is encrypted by the Arnold map. Then, DCT is applied to the encrypted watermark image and afterwards, the DWT prior to SVD is applied to it. The same steps are applied to the host image. The watermark image's singular values are then embedded into the host image's singular values. The method has better imperceptibility as PSNR is 57.63 dB. Also, the method proves robustness against WF, AF, MF, SPN, and rotation attacks. But, GN, SN, PN, cropping, scaling, resizing, hybrid attacks, and watermark embedding capacity are not observed by this method. Another hybrid discrete Fourier transform (DFT) and SVD-based method is proposed by [PERSON] and [PERSON] (2021) in 2021, where the logistic chaotic map is used for security. The method has a PSNR of 50.91 dB, which proves better imperceptibility and is robust against the filter, geometric, hybrid, image sharpening, Gamma correction, HE, and image blur attacks. Also, the watermark embedding capacity is 20,480 bits. But, it shows a weaker performance than other non-DFT-based methods. Another fusion-based blind method DWT-DCT-SVD is proposed in the paper (2021). The Arnold map is employed in this technique to guarantee the security of the watermark image. Experimental results show that PSNR is 44.05 dB, and the method is robust against AF, MF, Gaussian blurring, JPEG compression, JPEG 2000, HE, resizing, and cropping attacks. But, the method is less robust against SPN and GN attacks, and the method has a large computational complexity due to fusion. Also, hybrid, scaling, GF, PN attacks, and embedding capacity are not observed. In the scheme [PERSON] et al., 2021 (2021), another hybrid DCT-DWT-based watermarking method is proposed. At first, the watermark image is encrypted by the Arnold map. Then, 2L DWT is applied to the host image and extracted from the LH sub-band. Then, LH is divided into blocks, and DCT is applied to each block. Then, the watermark is embedded into the modified DC coefficients of the host image. Experimental results show high PSNR (>69 dB) and strong robustness against cropping, scaling, adaptive filtering, HE, SPN, GN, and sharpening attacks. Also, the method requires less time (0.97 s) to execute without attacks. But, rotation, resizing, MF, AF, LPGF, SN, and hybrid attacks are not observed. Also, the capacity is not calculated. Another decomposition-based fragile image watermarking is proposed by the scheme by [PERSON] et al., 2021 (2020), where the QR technique decomposes the watermark image. Fourier transform (FT) is applied to the host image, and then QR is applied to it. Then, coefficients of the R matrix of the watermark image are embedded into the coefficients of the R matrix of the host image. The method obtains a high PSNR which is greater than 62 dB.