## 4 Evaluation and Discussion
### Image Quality Analysis
#### 4.4.2 Cover vs. Stego Image Comparison  
An effective image steganography system should generate stego images that appear visually indistinguishable from their cover images, rendering the differences imperceptible to the human eye as illustrated in Table 6. To discern changes at the pixel level, the images in Table 6 are magnified and presented in Table 7. Upon magnification, differences become apparent, with observed variations in pixel values between the stego and cover images. Nevertheless, these subtle alterations are unlikely to raise suspicion for a human observer. This aligns with the MSE and PSNR results detailed in Tables 8 and 9, respectively. \begin{table}
\begin{tabular}{c c c c c} \hline
**No.** & **Test Type** & \(P_{value}\) & **Proportion** & **Result** \\ \hline
11. & Approximate Entropy & 0.066882 & 1 & Pass \\
12. & Random Excursions & - & 1 & Pass \\
13. & Random Excursions Variant & - & 1 & Pass \\
14. & Serial & 0.534146 & 0.9 & Pass \\
15. & Linear Complexity & 0.350485 & 1 & Pass \\ \hline \end{tabular}
\end{table} 
Table 5: _Cont._ \begin{table}
\begin{tabular}{c c c} \hline \hline
**Scenario** & **Cover Image** & **Stego Image** \\ \hline rainbow to lenna & & \\ \hline monarch to malamute & & \\ \hline monarch to malamute & & \\ \hline \hline \end{tabular}
\end{table} 
Table 6: Cover image quality vs. stego image quality. \begin{table}
\begin{tabular}{c c c c} \hline \hline
**Scenario** & **Cover Image** & **Stego Image** \\ \hline rainbow to lenna & & & \\ \hline rainbow to lenna & & & \\ \hline rainbow to lenna & & & \\ \hline rainbow to malamute & & & \\ \hline \hline \end{tabular}
\end{table} 
Table 7: Cover image quality vs. stego image quality (zoomed in). Table 8 shows the MSE between the cover image (left side of the arrow) and the stego image (entire scenario) for each color channel of the pixels and the aggregate. In each scenario, the MSE for each channel is small, i.e., below 1.0. Similarly, the aggregate MSE is below 10.0. This means that pixel values in the stego image have very small differences from the pixel values in the cover image. Table 9 shows the PSNR between the cover image and the stego image for each color channel of the pixels and the aggregate. In each scenario, the PSNR for each channel is very good, i.e., above 40 dB. Similarly, the aggregate PSNR is above 40 dB for all but one scenario. This means that, similar to the MSE results, pixel values in the stego image have very small differences from the pixel values in the cover image. Table 10 shows a more thorough MSE and PSNR analyses between for several other images and with different embedding methods. For this, a comparison with the LSB-1, LSB-2, LSB-4 [11], and LSB 3-3-2 is conducted. We can see that similar results are obtained as shown in Table 9.  
We can also see that the LSB 3-3-2 embedding technique has worse MSE and PSNR values compared to LSB-1 and LSB-2 but is better than LSB-4. This is because LSB-1 and LSB-2 only embed the bits of the secret image into the last one and two bits of the cover image pixels, respectively, which can result in stego images with less noticeable visual differences.