\begin{figure}
    \centering
    \begin{subfigure}{0.3\textwidth}
        \caption{小光圈图片}
       \includegraphics[width = \textwidth]{figures/defocus/0_29_inf.png}\\
        \includegraphics[width = \textwidth]{figures/defocus/0_27_inf.png}
        \label{fig:1}
    \end{subfigure}
    \hfill
    \begin{subfigure}{0.3\textwidth}
        \caption{大光圈图片}
        \includegraphics[width = \textwidth]{figures/defocus/0_29_hr.png}\\
        \includegraphics[width = \textwidth]{figures/defocus/0_27_hr.png}
        \label{fig:2}
    \end{subfigure}
    \hfill
    \begin{subfigure}{0.3\textwidth}
        \caption{模拟大光圈图片}
        \includegraphics[width = \textwidth]{figures/defocus/0_29_sr.png}\\
        \includegraphics[width = \textwidth]{figures/defocus/0_27_sr.png}
        \label{fig:3}
    \end{subfigure}
    \caption{散焦训练集采样结果}
    \label{fig:appendix-defocus}
\end{figure}