从坐标中提取 x/y 值（以厘米为单位）

Question

我想提取以 cm 为单位的 x/y 坐标。下面的示例将其提取为 pt。

\documentclass[]{standalone}
\usepackage{tikz}
\usetikzlibrary{calc}
\begin{document}
\begin{tikzpicture}
\coordinate (A) at (2,3);
\path let \p1=(A) in node[draw,circle,inner sep=5pt,label=above:{\x1,\y1}] at (A) {};
\end{tikzpicture}
\end{document}

我怎样才能获得 2,3 作为标签？

Answer 1

您可以使用\fpeval。该\ptto命令需要将单位作为第一个强制参数，因此您可以使用不同的参数。可选参数是要四舍五入的小数位数。

\documentclass[border=4]{standalone}
\usepackage{tikz}
\usetikzlibrary{calc}

\NewExpandableDocumentCommand{\ptto}{O{2}mm}{%
  \fpeval{round((#3)/(1#2),#1)}%
}

\begin{document}

\begin{tikzpicture}
  \coordinate (A) at (2,3);
  \path let \p1=(A) in node[
    draw,
    circle,
    inner sep=5pt,
    label=above:{\ptto{cm}{\x1},\ptto{cm}{\y1}}
  ] at (A) {};
\end{tikzpicture}

\end{document}

也许您想要以缩放点为单位的长度……

\documentclass[border=4]{standalone}
\usepackage{tikz}
\usetikzlibrary{calc}

\NewExpandableDocumentCommand{\ptto}{O{2}mm}{%
  \fpeval{round((#3)/(1#2),#1)}%
}

\begin{document}

\begin{tikzpicture}
  \coordinate (A) at (2,3);
  \path let \p1=(A) in node[
    draw,
    circle,
    inner sep=5pt,
    label=above:{\ptto[0]{sp}{\x1},\ptto[0]{sp}{\y1}}
  ] at (A) {};
\end{tikzpicture}

\end{document}

Answer 2

代码

\documentclass[border=10pt]{standalone}
\usepackage{tikz}
\usetikzlibrary{calc, math}
\makeatletter
% transform a dimension (in pt) into a dimensionless number
\newcommand{\strippt}{\strip@pt\dimexpr}
\makeatother

\begin{document}
\begin{tikzpicture}
  \coordinate (A) at (2,3);
  \path let \p1=(A),
  \n1 = {\x1*1pt/1cm},
  \n2 = {\y1*1pt/1cm},
  in
  node[draw, circle, inner sep=5pt,
  label=above:{\strippt(\n1),\strippt(\n2)}] at (A) {};
\end{tikzpicture}
\end{document}

Answer 3

您可以使用\pgfmathparse来删除单位。从点到厘米的转换因子是 .03514。您可以使用\pgfmathprintnumber来避免舍入误差。

\documentclass[]{article}
\usepackage{tikz}
\usetikzlibrary{calc}
\begin{document}
\begin{tikzpicture}
\coordinate (A) at (2,3);
\path let \p1=(A) in node[draw,circle,inner sep=5pt,label=above:{\pgfmathparse{.03514*\x1}\pgfmathprintnumber{\pgfmathresult},\pgfmathparse{.03514*\y1}\pgfmathprintnumber{\pgfmathresult}}] at (A) {};
\end{tikzpicture}
\end{document}