如何让图片准确定位在框架的右下角？

Question

我在使用 pgf 包时遇到了一个问题。每次我想要改变坐标时，图片就会消失。我不知道为什么。这是我的代码和输出。

\documentclass{beamer}
\mode<presentation> {
\usetheme{Berlin}
}
\usepackage{graphicx} 
\usepackage{booktabs} 
\usepackage{color}
\usepackage{mathtools}
\usepackage{multirow}\usepackage{mathrsfs}
\usepackage{hyperref}
\usepackage{fancybox}
\usepackage{pgf}

\def\EE{\mathscr{E}}\def\FF{\mathscr{F}}
\def\IP{\mathbb{P}}\def\IE{\mathbb{E}}
\def\BB{\mathscr{B}}
\def\IR{\mathbb{R}}
\def\ss{\mathsf{s}}
\def\df{\mathrm{d}}
\setbeamertemplate{background}{\includegraphics[height=\paperheight]
{bg.jpg}}
\usecolortheme{dove}
\setbeamerfont{frametitle}{series=\bfseries}
\setbeamercolor{frametitle}{fg=white,bg=black}
\setbeamercolor{title}{fg=white,bg=black}
\begin{document}
\begin{frame}
\frametitle{Markov processes and Dirichlet forms}
\begin{itemize}
\item $(T_t)\leftrightarrows (L,D(L)\rightleftarrows (\EE,\FF)$
\item $0\le T_tu\le 1$ for any $0\le u\le 1$ $\rightleftarrows$ $(\EE,\FF)$ 
is Markov
\end{itemize}
\pgfputat{\pgfxy(0,0)}{\pgfbox[left,base]{\pgfimage[width=1cm]{logo.jpg}}}
\end{frame}
\end{document}

但如果我改变坐标，例如

\documentclass{beamer}
\mode<presentation> {
\usetheme{Berlin}
}
\usepackage{graphicx} 
\usepackage{booktabs} 
\usepackage{color}
\usepackage{mathtools}
\usepackage{multirow}\usepackage{mathrsfs}
\usepackage{hyperref}
\usepackage{fancybox}
\usepackage{pgf}

\def\EE{\mathscr{E}}\def\FF{\mathscr{F}}
\def\IP{\mathbb{P}}\def\IE{\mathbb{E}}
\def\BB{\mathscr{B}}
\def\IR{\mathbb{R}}
\def\ss{\mathsf{s}}
\def\df{\mathrm{d}}
\setbeamertemplate{background}{\includegraphics[height=\paperheight]
{bg.jpg}}
\usecolortheme{dove}
\setbeamerfont{frametitle}{series=\bfseries}
\setbeamercolor{frametitle}{fg=white,bg=black}
\setbeamercolor{title}{fg=white,bg=black}
\begin{document}
\begin{frame}
\frametitle{Markov processes and Dirichlet forms}
\begin{itemize}
\item $(T_t)\leftrightarrows (L,D(L)\rightleftarrows (\EE,\FF)$
\item $0\le T_tu\le 1$ for any $0\le u\le 1$ $\rightleftarrows$ $(\EE,\FF)$ 
is Markov
\end{itemize}
\pgfputat{\pgfxy(0,1cm)}{\pgfbox[left,base]{\pgfimage[width=1cm]{logo.jpg}}}
\end{frame}
\end{document}

就变成这样了。

我不知道它是怎么产生的。有人能回答我吗？非常感谢！