如何在图片上画阴影

Question

我有以下示例，我想知道为什么它不起作用：

\documentclass[tikz]{standalone}

\usetikzlibrary{positioning}
\usetikzlibrary{calc}
\usetikzlibrary{quotes}
\usetikzlibrary{shadows}

\RequirePackage{luatex85}

\begin{document}
\newcommand\unit{1.2cm}
\begin{tikzpicture}[
  pics/limiter/.style={
    code={
      \draw[black!50,very thin] (-0.45*\unit,0) -- (0.45*\unit,0);
      \draw[black!50,very thin] (0,-0.45*\unit) -- (0,0.45*\unit);
      \draw (0.5*\unit,0.5*\unit) -- (0.5*\unit,-0.5*\unit) --
            (-0.5*\unit,-0.5*\unit) -- (-0.5*\unit,0.5*\unit) -- cycle;
      \draw (-0.4*\unit,-0.4*\unit) -- (-0.25*\unit,-0.4*\unit) --
            (0.25*\unit,0.4*\unit) -- (0.4*\unit,0.4*\unit); 
      \coordinate (-north) at (0,0.5*\unit);
      \coordinate (-west) at (-0.5*\unit,0);
      \coordinate (-south) at (0,-0.5*\unit);
      \coordinate (-east) at (0.5*\unit,0);
    },
    drop shadow={shadow xshift=.3ex,shadow yshift=-.3ex}
  }
] 
  \pic[fill=yellow!50] (lim) at(0,0) {limiter};
\end{tikzpicture}
\end{document}

只有阴影才看起来像这样

Answer 1

使用标准节点绘制限制器更简单、更灵活（关于节点名称、定位等）。除此之外，\pic似乎无法使用drop shadow路径选项。

\documentclass[tikz, margin=3mm]{standalone}
\usetikzlibrary{shadows}


\begin{document}
\newcommand\unit{1.2cm}
    \begin{tikzpicture}[
limiter/.style = {shape=rectangle, draw,
                  fill=#1, drop shadow,
                  minimum size=\unit, outer sep=0mm,
    path picture={%
      \draw[black!50,very thin] (-0.45*\unit,0) -- (0.45*\unit,0);
      \draw[black!50,very thin] (0,-0.45*\unit) -- (0,0.45*\unit);
      \draw (-0.40*\unit,-0.4*\unit) -- (-0.25*\unit,-0.4*\unit) --
            ( 0.25*\unit, 0.4*\unit) -- ( 0.40*\unit, 0.4*\unit);
                },% end path picture
               },% end of limiter
limiter/.default = white
                ]
\node[limiter] (lim) at (0,0) {};
\node[limiter=yellow] (lim) at (2,0) {};
    \end{tikzpicture}
\end{document}