## 4 Experimental Results and Discussion
### Comparative Study  
The performance of the proposed scheme is further validated by comparing it with recent state-of- the-art DIW schemes [18; 23; 27; 28; 31; 32] in terms of imperceptibility, robustness, embedding rate, security, and fitness function. Performance comparison has been done with a non-blind scheme proposed by [PERSON] and [PERSON] [18] and blind schemes proposed by [PERSON] [31], [PERSON] and [PERSON] [32], [PERSON] and [PERSON] [27], and [PERSON] et al. [23]. The scheme proposed in [18] uses PC for embedding watermark bits in the DWT-SVD domain. Arnold map is used for security, and scaling factor is optimized with ABC. This scheme suffers from low imperceptibility, robustness, and security. The Hadmaard transform based scheme is proposed in [31]. This scheme uses DDFA for scaling \begin{table}
\begin{tabular}{l l} \hline \hline
**Operations** & **Computational Cost** \\ \hline
1-level 2D inverse IWT transform & \(O(2 MN)\) \\ SVD decomposition & \(O(2 MN^{2}+2N^{3})\) \\ SVD re-composition & \(O(2 min[M,N]MN)\) \\ ISF Optimization & O(MN) \\ Adaptive block selection & \(O(MN)\) \\ Determination of adaptive embedding position using BBS & \(O(log(log~{}m))\) \\ \hline \hline \end{tabular}
\end{table} 
Table 8: Computational time of major algorithmic steps for the cover image of size \(M\times N\). \begin{table}
\begin{tabular}{l c c c c c} \hline \hline
**Grayscale** & **Embedding Time** & **Extraction Time** & **Color** & **Embedding Time** & **Extraction Time** \\
**Image** & **(s)** & **(s)** & **Image** & **(s)** & **(s)** \\ \hline Lena & 1.919406 & 1.056093 & Koala & 1.378239 & 0.987560 \\ Baboon & 1.465614 & 0.915152 & Penguins & 1.686724 & 0.977352 \\ Lighthouse & 1.553255 & 1.025732 & Tulips & 1.433371 & 0.831694 \\ Desert & 1.324148 & 0.985283 & Tiffany & 1.277285 & 0.900063 \\ Grain & 1.264661 & 0.973439 & Splash & 1.244865 & 0.907733 \\ MRI & 1.470474 & 0.715602 & Skin & 1.273823 & 0.616617 \\ \hline Average & 1.526388 & 0.995216 & Average & 1.382384 & 0.870169 \\ \hline \hline \end{tabular}
\end{table} 
Table 9: Embedding and extraction time (seconds) of cameraman watermark image with different test cover images. factor optimization. Watermark is embedded by adjusting Hadmaard coefficients, and it overlooked watermark security. The scheme proposed in [32] uses an LWT based adaptive embedding approach using a d-sequence. Arnold map is used for watermark security. This scheme has a lower embedding rate than other schemes [18; 23; 27]. A DCT based adaptive embedding scheme is proposed in [27], and it generates embedding blocks using an LGBA machine learning approach. This scheme also ignored watermark security. The scheme proposed in [23] uses IWT-SVD transform, and it shows lower NC values for rotation, JPEG compression, Gaussian filter, and Median filtering attacks. This scheme has high imperceptibility, security, and embedding rate at the cost of robustness. Table 10 shows a comparative study of watermarking parameters for the proposed scheme and schemes in comparison. **Imperceptibility Comparison:** Imperceptibility performance of the proposed scheme is compared with schemes proposed in [18; 23; 27; 31; 32] using PSNR. For comparative study, two popular test images \"Lena\" and \"Baboon\" are considered. Figure 15 shows PSNR values of the proposed scheme and schemes in [18; 23; 27; 31; 32] for \"Lena\" and \"Baboon\". The PSNR values in Figure 15 indicate that the proposed scheme has higher imperceptibility than schemes in [18; 23; 27; 31; 32] with a higher/equal embedding rate. From this, it can be claimed that the proposed scheme has higher imperceptibility than schemes in comparison.