## 2 Related Literature and Problem Statement
### Literature Review  
There exists a lot of research work on hybrid domain image watermarking methods. A color image watermarking method is designed by [PERSON] et al., 2017 [PERSON] et al. (2017) based on wavelet and QR decomposition. Two-level (2L) DWT, QR decomposition, Chirp Z-Transform (CZT), and SVD are used to embed the watermark image into the cover (or host) image. The method ensures better imperceptibility and high robustness against various attacks like gamma correction, flipping, image blur, contrast enhancement, histogram equalization (HE), Gaussian noise (GN), salt-and-pepper-noise (SPN), and image sharpening. But, this method is less robust against cropping, scaling, and JPEG compression attacks. Moreover, the security of the watermark image and embedding capacity into the host image are not observed. [PERSON] et al. (2018) proposed another robust and secure color image watermarking method by combining DWT, SVD, and QR codes. At first, 2L DWT is applied on the color cover or host image prior to dividing it into blocks. Then, SVD is applied to each block and extracted the singular values. Then, the same steps are done to the QR code as a watermark image. After that, the method embeds the singular values of the watermark image into the singular values of the host image. The method is robust against GN, SPN, and median filter (MF) attacks. But, other requirements like imperceptibility, security, and embedding capacity are not analyzed. Also, geometric and other signal-processing attacks are not observed. Therefore, in the scheme [PERSON] et al., 2018 [PERSON] et al. (2018), another hybrid domain image watermarking method is proposed that combines NSCT, DCT, and SVD to ensure better imperceptibility and high robustness against geometric and other attacks. NSCT, DCT, and SVD are applied one after another to both host and watermark images. Here, singular values of the watermark image are embedded into the singular values of the host image. The watermarked image is generated after performing inverse transformations. The method is robust against JPEG compression, average filter (AF), Gaussian filter (GF), MF, GN, HE, Gaussian blur, motion blur, SPN, rotation, scaling, and resizing attacks. But, the method does not observe security and calculate the watermark embedding capacity into the host image. [PERSON] et al. (2018) proposed another robust and secure hybrid domain method that combines sharp frequency localized contourlet transform (SFLCT) and SVD. Experimental results show that PSNR is 45.85 dB, which makes the watermarked image less noticeable. Also, the method is robust against Gamma correction, JPEG compression, GN, SPN, SN, sharpening, MF, Wiener filter (WF), HE, scaling, rotation, cropping, copy attack, cutting, and shearing attacks. But, they do not use any security method and compute the host image's capability for watermark embedding. In 2018, [PERSON] et al. (2018) proposed another DWT, all-phase discrete cosine biorthogonal transform (APDCBT), and an SVD-based hybrid image watermarking method. At first, DWT, APDCBT, and SVD are applied to the cover image one after another. Watermark is inserted into the singular values of the host image. The generated watermarked image seems similar to the host image as PSNR is 101.97 dB. The method proves robustness against SPN, JPEG compression, GN, scaling, MF, AF, rotation, contrast enhancement, and brightness adjustment attacks. The method is resistant to hybrid attacks as well, which is an additional feature of this method. The embedding capacity is 2048 bits. But, this method does not consider the false-positive-detection (FPD)problem. Also, any security technique is not used to ensure the security of the watermark image. [PERSON] et al. (2015) proposed another hybrid image watermarking method based on DWT, Hessenberg decomposition (HD), and SVD. To ensure that robustness and imperceptibility are properly balanced, the Fruit fly optimization algorithm is used to determine the optimized scaling factor.