## 6 Experimental Results and Discussion
### Comparison with State-of-the-Art Schemes
\begin{table}
\begin{tabular}{c c c c c c c c c c} \hline \hline  & **10\%** & **20\%** & **30\%** & **40\%** & **50\%** & **60\%** & **70\%** & **80\%** & **90\%** \\ \hline SR-HTR & 33.29 & 30.20 & 28.15 & 26.70 & 25.57 & 24.38 & 23.03 & 21.32 & 18.88 \\ [PERSON] [36] & 36.12 & 32.47 & 29.10 & 25.89 & 23.07 & 20.26 & 17.75 & 15.54 & 13.58 \\ [PERSON] [23] & 31.37 & 29.33 & 23.21 & 20.33 & 17.73 & 14.09 & 12.13 & 10.15 & 8.78 \\ [PERSON] [2] & 23.79 & 18.85 & 15.71 & 13.36 & 11.55 & 9.98 & 8.67 & 7.54 & 6.52 \\ [PERSON] [24] & 25.29 & 19.98 & 16.77 & 14.41 & 12.67 & 11.27 & 10.16 & 9.25 & 8.43 \\ [PERSON] [10] & 34.70 & 26.87 & 21.80 & 18.13 & 15.25 & 12.79 & 10.73 & 8.94 & 7.33 \\ \hline \hline \end{tabular}
\end{table} 
Table 14: Comparison of average PSNR-HSV-M for the reconstruction of the test images with alteration rates between 10% and 90%. \begin{table}
\begin{tabular}{c c c c c c c c c c} \hline \hline  & **10\%** & **20\%** & **30\%** & **40\%** & **50\%** & **60\%** & **70\%** & **80\%** & **90\%** \\ \hline SR-HTR & 33.29 & 30.20 & 28.15 & 26.70 & 25.57 & 24.38 & 23.03 & 21.32 & 18.88 \\ [PERSON] [36] & 36.12 & 32.47 & 29.10 & 25.89 & 23.07 & 20.26 & 17.75 & 15.54 & 13.58 \\ [PERSON] [23] & 31.37 & 29.33 & 23.21 & 20.33 & 17.73 & 14.09 & 12.13 & 10.15 & 8.78 \\ [PERSON] [2] & 23.79 & 18.85 & 15.71 & 13.36 & 11.55 & 9.98 & 8.67 & 7.54 & 6.52 \\ [PERSON] [24] & 25.29 & 19.98 & 16.77 & 14.41 & 12.67 & 11.27 & 10.16 & 9.25 & 8.43 \\ [PERSON] [10] & 34.70 & 26.87 & 21.80 & 18.13 & 15.25 & 12.79 & 10.73 & 8.94 & 7.33 \\ \hline \hline \end{tabular}
\end{table} 
Table 11: Comparison of objective quality metrics for the reconstruction of Kodak-15 using alteration rates between 20% and 90%. \begin{table}
\begin{tabular}{c c c c c c c c c} \hline \hline  & **10\%** & **20\%** & **30\%** & **40\%** & **50\%** & **60\%** & **70\%** & **80\%** & **90\%** \\ \hline SR-HTR & 35.80 & 32.72 & 30.63 & 29.25 & 28.14 & 27.06 & 26.01 & 24.82 & 23.08 \\ [PERSON] [36] & 37.28 & 33.97 & 31.20 & 28.71 & 26.38 & 23.99 & 21.77 & 19.79 & 18.01 \\ [PERSON] [23] & 31.62 & 29.32 & 23.75 & 20.96 & 18.41 & 14.92 & 12.98 & 10.99 & 9.63 \\ [PERSON] [2] & 26.74 & 21.76 & 18.61 & 16.30 & 14.54 & 13.04 & 11.79 & 10.70 & 9.71 \\ [PERSON] [24] & 26.34 & 21.05 & 17.94 & 15.71 & 14.02 & 12.57 & 11.36 & 10.33 & 9.40 \\ [PERSON] [10] & 35.22 & 28.68 & 23.98 & 20.59 & 17.92 & 15.61 & 13.67 & 11.98 & 10.46 \\ \hline \hline \end{tabular}
\end{table} 
Table 12: Comparison of average PSNR for the reconstruction of the test images with alteration rates between 10% and 90%. The last evaluation is the comparison of the reconstruction proficiency of multiple and irregular alterations. This test was performed using the modifications illustrated in Figure 12. Their corresponded reconstructed images are shown in Table 15. The images' alteration rates are Kodak-4 at 85.65%, Kodak-10 at 26.42%, Kodak-17 at 74.36% and Kodak-18 at 30.97%. The PSNR, SSIM and PSNR-HVS-M values of the reconstructed image compared with the original ones are reported in Table 16.  
On one hand, it can be observed that the proposed SR-HTR method presents the best objective quality for each reconstructed image. On the other hand, the method given by [23] resulted in better SSIM values for Kodak-10 because the alteration rate is low. However, the visual quality of the reconstructed Kodak-10 given in Table 15 for the proposed method represents an admissible reconstruction. As can be noticed in Tables 9-16, the novel SR-HTR method demonstrated an excellent performance compared with the other state-of-the-art schemes in terms of regular attacks (as seen in Tables 9-14) and multiple and irregular attacks (shown in Tables 15 and 16). \begin{table}
\begin{tabular}{c c c c c} SR-HTR & [PERSON] [36] & [PERSON] [23] & [PERSON] [2] & [PERSON] [24] & [PERSON] [10] \\ Kodak-4 & & & & & \\ Kodak-10 & & & & & \\ Kodak-18 & & & & & \\ Kodak-18 & & & & & \\ Kodak-18 & & & & & \\ Kodak-18 & & & & & \\ \end{tabular}
\end{table}