为什么坐标被移动但没有被缩放

Question

我正在尝试在监视区域上绘图

\documentclass[multi={tikzpicture,wrapper}]{standalone}

\usepackage{amsfonts}
\usepackage{tikz}
\usetikzlibrary{calc,spy}

\begin{document}
    \begin{tikzpicture}
        \pgfmathsetmacro{\radius}{8}
        \pgfmathsetmacro{\largeradius}{2 * \radius}
        \pgfmathsetmacro{\hugeradius}{2.6 * \radius}
        \coordinate (center) at (0, 0);

        % create sector
        \pgfmathsetmacro{\addangle}{ 6 }        
        \pgfmathsetmacro{\startangle}{90 - \addangle}
        \pgfmathsetmacro{\endangle}{\startangle + 2 * \addangle}

        \pgfmathsetmacro{\zoominratio}{4.5}
        \pgfmathsetmacro{\preferrableSize}{5}

        \pgfmathsetmacro{\startradius}{0.35 * \radius}
        \pgfmathsetmacro{\endradius}{0.4 * \radius}

        \coordinate (a) at (\startangle:\startradius);
        \coordinate (c) at (\endangle:\endradius);
        \coordinate (spypoint) at ($(a)!.5!(c)$);

        \begin{scope}[spy using outlines]
            % create dA
            \draw (a)
                arc (\startangle:\endangle:\startradius) 
                -- (c)
                arc (\endangle:\startangle:\endradius)
                -- cycle;


            % Spy
            \spy[blue, circle, draw, height = \preferrableSize cm, width = \preferrableSize cm, magnification = \zoominratio, connect spies] 
                on (spypoint) in node (spyglass) at (4,3);
        \end{scope}

        \begin{scope}[shift={(spyglass.center)}, scale = \zoominratio]
            \coordinate (trypoint) at ($(c)-(spypoint)$);
            \draw[red] (trypoint) circle (.1 cm);
        \end{scope}

    \end{tikzpicture}
\end{document}

这给了我一个形象

我的问题是关于下一行

        \begin{scope}[shift={(spyglass.center)}, scale = \zoominratio]
            \coordinate (trypoint) at ($(c)-(spypoint)$);
            \draw[red] (trypoint) circle (.1 cm);
        \end{scope}

红色圆圈是为了调试目的。（trypoint）坐标是在望远镜区域内计算的，即它被移动了，但它不在“梯形”的顶点上，即没有缩放。为什么？

Answer 1

我认为你对所做事情的印象并不完全正确scale。你需要真正将坐标乘以\zoominratio才能得到（我认为）你想要的。

\documentclass[multi={tikzpicture,wrapper}]{standalone}

\usepackage{amsfonts}
\usepackage{tikz}
\usetikzlibrary{calc,spy}

\begin{document}
    \begin{tikzpicture}
        \pgfmathsetmacro{\radius}{8}
        \pgfmathsetmacro{\largeradius}{2 * \radius}
        \pgfmathsetmacro{\hugeradius}{2.6 * \radius}
        \coordinate (center) at (0, 0);

        % create sector
        \pgfmathsetmacro{\addangle}{ 6 }        
        \pgfmathsetmacro{\startangle}{90 - \addangle}
        \pgfmathsetmacro{\endangle}{\startangle + 2 * \addangle}

        \pgfmathsetmacro{\zoominratio}{4.5}
        \pgfmathsetmacro{\preferrableSize}{5}

        \pgfmathsetmacro{\startradius}{0.35 * \radius}
        \pgfmathsetmacro{\endradius}{0.4 * \radius}

        \coordinate (a) at (\startangle:\startradius);
        \coordinate (c) at (\endangle:\endradius);
        \coordinate (spypoint) at ($(a)!.5!(c)$);

        \begin{scope}[spy using outlines]
            % create dA
            \draw (a)
                arc (\startangle:\endangle:\startradius) 
                -- (c)
                arc (\endangle:\startangle:\endradius)
                -- cycle;


            % Spy
            \spy[blue, circle, draw, height = \preferrableSize cm, width = \preferrableSize cm, magnification = \zoominratio, connect spies] 
                on (spypoint) in node (spyglass) at (4,3);
        \end{scope}

        \begin{scope}[shift={(spyglass.center)}, scale = \zoominratio]
            \coordinate (trypoint) at  ($\zoominratio*(c)-\zoominratio*(spypoint)$);
            \draw[red] (trypoint) circle (.1 cm);
        \end{scope}

    \end{tikzpicture}
\end{document}