5 如何将背景图片置于底部

感谢@u79794 和 TSE上的beamer高手samcarter_is_at_topanswers.xyz
可以考虑使用picture或者tikzpicture环境来定位图片位置，如下代码

\documentclass{beamer}
\usetheme{AnnArbor}
\usepackage[12pt]{ctex}
\usepackage{graphicx}
\usepackage{tikz}
\begin{document}
    \begin{frame}{Title}
        contents ...
    \end{frame}
    % 设置当前 frame 的背景图片
    \setbeamertemplate{background}{%
        % \begin{picture}(200,250) % <- bad solution to adjust by yrself
        %     \includegraphics[width=\paperwidth,height=.3\paperheight]{example-image}
        % \end{picture}
        \begin{tikzpicture}[overlay, remember picture]
            % maybe a better solution to position the image
            \node[yshift=6em] at (current page.south) {\includegraphics[width=\paperwidth,height=.3\paperheight]{example-image}};
        \end{tikzpicture}
    }
    \begin{frame}
        \begin{center}
            {\LARGE Thanks for your attention!}
        \end{center}
    \end{frame}
    % 重置背景模板
    \setbeamertemplate{background}{}
    \begin{frame}
        \begin{center}
            {\LARGE Thanks for your attention!}
        \end{center}
    \end{frame}
\end{document}