# Camera-Based Vital Sign Estimation Techniques and Mobile App Development
## 3 Results
### Mobile Application  
The proposed noncontact bio-signal detection technique was implemented as a mobile app which measured, recorded, and analyzed the user's bio-signals using a smartphone camera and included a statistical data generation function. Considering the need for user convenience, interface development, and easy maintenance, React Native [21], a cross-platform development framework, was used for mobile application development rather than native platform development, as shown in Figure 18.  
The user data management in the developed application was designed to be suitable for mobile storage-based data recording/management. The basic structure consists of a String-based data structure of Key: Value (Object) in JSON format, and will be designed in a form applicable to the Restful web service, non-normalized NoSQL databases, and SQL databases in the future.  
The developed app is composed of login, home, measurement, and history screens, as shown in Figure 19. Currently, only the HR and SpO2 functions are active. The home screen  
\begin{table}
\begin{tabular}{c c c c c} \hline \hline \multirow{2}{*}{**Performance Criteria**} & \multicolumn{4}{c}{**Methods**} \\ \cline{2-5}  & **[PERSON] et al. [13]** & **[PERSON] et al. [14]** & **[PERSON] et al. [15]** & **CA-POS (Proposed)** \\ \hline MSE & 1.18 & 1.25 & 0.98 & 0.86 \\ RMAE & 1.83 & 1.97 & 1.57 & 1.23 \\ \hline \hline \end{tabular}
\end{table}
Table 7: Performance comparison of four SpO2 detection algorithms.  
Figure 17: (a) Linear relationship between and (b) Bland–Altman plot of measured RR and RR estimated based on image sequences.  
\begin{table}
\begin{tabular}{c c c c c} \hline \hline \multirow{2}{*}{**Performance Criteria**} & \multicolumn{4}{c}{**Methods**} \\ \cline{2-5}  & **[PERSON] et al. [16]** & **[PERSON] et al. [17]** & **[PERSON] et al. [18]** & **CA-POS (Proposed)** \\ \hline MSE & 1.12 & 1.34 & 1.21 & 0.98 \\ RMAE & 1.68 & 2.16 & 1.98 & 1.55 \\ \hline \hline \end{tabular}
\end{table}
Table 8: Performance comparison of four RR detection algorithms.  
consists of user information, a measurement calendar, and health data. When measured health signal data is added to the measurement calendar, a blue circle is displayed on the date. When a user selects the displayed date, the measured data appears in a health data tab. The health data can be scrolled through to the left and right, with up to five measurements per day, and five toggle buttons were created accordingly. The measurement screen's functions include (1) health data measurement, (2) result viewing, and (3) detailed result viewing.  
When viewing the history screen, the history over 1 day, 1 week, 1 month, and 6 months appears. The daily history view shows measured data as a blue circle on a calendar, just like the home screen calendar. When a date with data is selected, the user is taken to the measurement result screen. When the detailed measurement result view is selected, the user is taken to the detailed measurement result screen.  
Figure 19: GUI of developed app: (**a**) login, (**b**) home, (**c**) measurement, and (**d**) history screens.  
Figure 18: System resource usage and configuration diagram of the developed app.