TikZ - 确定完成的 TikZ 图片的厘米尺寸

Question

我想以某种方式以编程方式确定 TikZ 图片的大小。有办法吗？这是一个简单的 MWE，我可以通过了解块大小并计算它们之间的节点距离来估计尺寸约为 8cm x 11cm。但更复杂的 TikZ 图片会使估计最终尺寸变得更加困难。

平均能量损失

\documentclass{standalone}
\usepackage{tikz}
\usetikzlibrary{positioning}

\begin{document}

\begin{tikzpicture}
    [bigblock/.style={draw, rectangle, minimum size=5cm},
     smallblock/.style={draw, rectangle, minimum size=2cm}
    ]
    
    \node [bigblock]                    (box1)  {};
    \node [bigblock, above=of box1]     (box2)  {};
    \node [smallblock, right=of box2]   (box3)  {};

\end{tikzpicture}

\end{document}

Answer 1

感谢评论中的@hpekristiansen 指出这个以 pt 为单位打印 TikZ 图片大小的答案：https://tex.stackexchange.com/a/137367/33388

我还将它与这里的答案结合起来，将 pts 转换为 cm：https://tex.stackexchange.com/a/137367/33388

平均能量损失

\documentclass[varwidth]{standalone}
\usepackage{tikz}
\usetikzlibrary{positioning}
%\show\pgfextractx

\newlength{\mywidth}
\newlength{\myheight}

\makeatletter
\newcommand{\pgfsize}[2]{ % #1 = width, #2 = height
    \pgfextractx{\@tempdima}{\pgfpointdiff{\pgfpointanchor{current bounding box}{south west}}
        {\pgfpointanchor{current bounding box}{north east}}}
    \global#1=\@tempdima
        \pgfextracty{\@tempdima}{\pgfpointdiff{\pgfpointanchor{current bounding box}{south west}}
            {\pgfpointanchor{current bounding box}{north east}}}
    \global#2=\@tempdima
}
\def\convertto#1#2{\strip@pt\dimexpr #2*65536/\number\dimexpr 1#1}
\makeatother

\begin{document}

\begin{tikzpicture}
    [bigblock/.style={draw, rectangle, minimum size=5cm, align=center},
     smallblock/.style={draw, rectangle, minimum size=2cm, align=center}
    ]
    
    \node [bigblock]            (box1)  {};
    \node [bigblock, above=of box1]     (box2)  {};
    \node [smallblock, right=of box2]   (box3)  {};

\pgfsize{\mywidth}{\myheight}
\end{tikzpicture}

% varwidth option was added to the standalone class options to allow for line breaks
Width = \convertto{cm}{\the\mywidth} cm\\
Height = \convertto{cm}{\the\myheight} cm

\end{document}