将参数传递给自定义框架选项

Question

跟进https://tex.stackexchange.com/a/174213/36296

长话短说：我想知道如何将参数传递给自定义框架选项。例如，向框架标题添加可自定义的图像。

---

并且应 MWE Leon Meier 的特别请求（我想知道如果没有它，samcarter 如何回答这个问题）：

\documentclass{beamer}
\usepackage{etoolbox}

\defbeamertemplate{frametitle}{mydefault}{%
  \insertframetitle%
}

\defbeamertemplate{frametitle}{imagetitle}{%
  \insertframetitle \includegraphics[width=0.1\textwidth]{example-image}%
}

\BeforeBeginEnvironment{frame}{%
  \setbeamertemplate{frametitle}[mydefault]%
}

\makeatletter
\define@key{beamerframe}{imagetitle}[true]{%
  \setbeamertemplate{frametitle}[imagetitle]%
}
\makeatother

\begin{document}

\begin{frame}
    \frametitle{bla}
  left
\end{frame} 

\begin{frame}[imagetitle]
    \frametitle{bla}
  right
\end{frame}

\begin{frame}
    \frametitle{bla}
  is left again
\end{frame}

\end{document}

Answer 1

\documentclass{beamer}
\usepackage{etoolbox}

\defbeamertemplate{frametitle}{mydefault}{%
  \insertframetitle%
}

\defbeamertemplate{frametitle}{imagetitle}[1]{%
  \insertframetitle \includegraphics[width=0.1\textwidth]{#1}%
}

\BeforeBeginEnvironment{frame}{%
  \setbeamertemplate{frametitle}[mydefault]%
}

\makeatletter
\define@key{beamerframe}{imagetitle}[true]{%
  \setbeamertemplate{frametitle}[imagetitle]{#1}%
}
\makeatother

\begin{document}

\begin{frame}
    \frametitle{bla}
  left
\end{frame} 

\begin{frame}[imagetitle=example-grid-100x100bp.pdf]
    \frametitle{bla}
  right
\end{frame}

\begin{frame}
    \frametitle{bla}
  is left again
\end{frame}

\end{document}