## 7 Performance Evaluation
### Experimental Results  
An experiment to compare the matched features of artwork was conducted with the following goals: (1) to evaluate the relation between the artwork size in the 360-degree image and the matched results; (2) to evaluate the relation between the position of the artwork in the 360-degree image and the matched results; and (3) to determine whether the proposed method improves the matched results. Of the experimental results from the feature matching, we only show the matched results from the SIFT, instead of reporting the results from all types of features. Figure 12a-c show the matched results between three 360-degree images and the artwork _Bedroom in Arles_. In the three 360-degree images on the left, the same artwork is displayed on the 79-inch monitor and was captured in the three different positions. We connected the matched features with yellow lines. In Figure 12a, the artwork is well matched, because it is large in size and close to the Equator. In Figure 12b, the camera is mounted higher and the monitor is shifted towards south, which increases the distortion. As a result, there are no matched features. In Figure 12c, the monitor is shifted further away from the Equator. The artwork is more seriously distorted and there are no matched features. The three matched results indicate that even though the artwork size is large, it cannot be recognized when it is not close to the Equator. \begin{table}
\begin{tabular}{c c c c} \hline \hline
**No.** & **Name** & **Image Size** & **File Size** \\ \hline
1 & _Cafe Terrace at Night_ & 1761 \(\times\) 2235 (300 DPI) & 641 KB \\
2 & _Lady with an Ernine_ & 3543 \(\times\) 4876 (300 DPI) & 3.33 MB \\
3 & _Family of Saltimbanques_ & 1394 \(\times\) 1279 (180 DPI) & 233 KB \\
4 & _Flowers in a Blue Vase_ & 800 \(\times\) 1298 (96 DPI) & 385 KB \\
5 & _[PERSON] at the Coronation of Charles_ & 1196 \(\times\) 1600 (96 DPI) & 460 KB \\
6 & _The Apotheosis of Homer_ & 1870 \(\times\) 1430 (300 DPI) & 3.1 MB \\
7 & _Romulus’ Victory over Acron_ & 2560 \(\times\) 1311 (72 DPI) & 384 KB \\
8 & _The Annunciation_ & 4057 \(\times\) 1840 (72 DPI) & 7.52 MB \\
9 & _The Last Supper_ & 5381 \(\times\) 2926 (96 DPI) & 3.19 MB \\
10 & _Mona Lisa_ & 7479 \(\times\) 11146 (72 DPI) & 89.9 MB \\
11 & _The Soup_ & 1803 \(\times\) 1510 (240 DPI) & 359 KB \\
12 & _The Soler Family_ & 2048 \(\times\) 1522 (72 DPI) & 1.91 MB \\
13 & _The Red Vineyard_ & 2001 \(\times\) 1560 (240 DPI) & 4.12 MB \\
14 & _Flowering orchard, surrounded by cypress_ & 2514 \(\times\) 1992 (600 DPI) & 2.89 MB \\
15 & _Flowering Orchard_ & 3864 \(\times\) 3036 (600 DPI) & 5.94 MB \\
16 & _Woman Spinning_ & 1962 \(\times\) 3246 (600 DPI) & 3.79 MB \\
17 & _Wheat Fields with Stacks_ & 3864 \(\times\) 3114 (600 DPI) & 6.01 MB \\
18 & _Bedroom in Arles_ & 767 \(\times\) 600 (96 DPI) & 40.9 KB \\
19 & _The Starry Night_ & 1879 \(\times\) 1500 (300 DPI) & 761 KB \\
20 & _A Wheat Field, with Cypresses_ & 3112 \(\times\) 2448 (72 DPI) & 7.22 MB \\ \hline \hline \end{tabular}
\end{table} 
Table 1: Original list of artworks. Figure 13a-c show matched results for the artwork _The Soup_. The artwork is displayed on the 32-inch monitor. Thus, the artwork size is substantially decreased. However, the features are well matched, because the artwork is close to the Equator, as shown in Figure 13a. In Figure 13b, the artwork is shifted towards the south, and there are no matched features. In Figure 13c, after shifting the artwork further away from the Equator, there is a false match. These three matched results suggest that the position has a larger effect on 360-degree image feature matching than the size. Figure 12: Matched results for the 79-inch monitor for three types of distortions. (**a**) Matched results for low distortion; (**b**) Matched results for middle distortion; (**c**) Matched results for high distortion. Figure 13: _Cont._  
Figure 14a-c show the matched results from the artwork _Flowering orchard_, _surrounded by cypress_. The artwork is displayed on the 23-inch monitor.