TikZ scale does not change the size of the arcs

Question

I have drawn the following figure:

As you can see, the arcs are too big for the page. So, I try to scale the image using [scale=0.5].

This works for the straight line segments perfectly. However, instead of scaling the arcs, TikZ does not change the size, but makes their centers closer to each other.

Here is a MWE for the first picture.

\documentclass[a4paper]{article}
\usepackage{tikz}
\tikzset{
    pics/carc/.style args={#1:#2:#3}{
        code={
            \draw[pic actions] (#1:#3) arc(#1:#2:#3);
        }
    }
}
\begin{document}


\begin{figure}[htbp]
    \centering
    \begin{tikzpicture}[scale=0.5]
    \tikzstyle{disk} = [draw, thick, circle,fill=none]
    \tikzstyle{center} = [draw,shape=rectangle,fill=blue]
    \tikzstyle{intersection} = [draw, circle ,fill=darkgray, inner sep=0.8mm]
    \node at (-6,0) {$A$};
    \node at (1,0) {$B$};
    \node at (-2,-6) {$C$};
    \draw[thick] (-8,0)  pic{carc=-100:50:60mm};
    \draw[thick] (2,0)  pic{carc=130:300:60mm};
    \draw[thick,red] (3.2,0)  pic{carc=130:300:60mm};
    \draw[thick] (-2,-14)  pic{carc=30:150:100mm};
    \draw[dashed] (-3,6)--(-3, -6);
    \draw[red] (-2.8,6)--(-2.8, -6);
    \draw[blue] (-2.2,6)--(-2.2, -6);
    \end{tikzpicture}
    \caption{Zoomed in}
    \label{fig:zoom}
\end{figure}

\end{document}

What can I do to scale the arcs as well?

Answer 1

You can use transform shape, see Section 17.7 of the TikZ & PGF Manual (for Version 3.0.1a).

By the way, look also at this post: Should \tikzset or \tikzstyle be used to define TikZ styles?.

\documentclass[a4paper]{article}
\usepackage{tikz}
\tikzset{
    pics/carc/.style args={#1:#2:#3}{
        code={
            \draw[pic actions] (#1:#3) arc(#1:#2:#3);
        }
    }
}
\begin{document}
    \begin{figure}[htbp]
        \centering
        \begin{tikzpicture}[
            scale=0.5, 
            transform shape,
            disk/.style={draw, thick, circle, fill=none},
            center/.style={draw,shape=rectangle,fill=blue},
            intersection/.style={draw, circle, fill=darkgray, inner sep=0.8mm}
            ]
            \node at (-6,0) {$A$};
            \node at (1,0) {$B$};
            \node at (-2,-6) {$C$};
            \draw[thick] (-8,0) pic{carc=-100:50:60mm};
            \draw[thick] (2,0) pic{carc=130:300:60mm};
            \draw[thick,red] (3.2,0) pic{carc=130:300:60mm};
            \draw[thick] (-2,-14) pic{carc=30:150:100mm};
            \draw[dashed] (-3,6) -- (-3,-6);
            \draw[red] (-2.8,6) -- (-2.8,-6);
            \draw[blue] (-2.2,6) -- (-2.2,-6);
        \end{tikzpicture}
        \caption{Zoomed in\label{fig:zoom}}
    \end{figure}
\end{document}

Or, if you don't want to change the node text size, add it only to the draw with the pics:

\documentclass[a4paper]{article}
\usepackage{tikz}
\tikzset{
    pics/carc/.style args={#1:#2:#3}{
        code={
            \draw[pic actions] (#1:#3) arc(#1:#2:#3);
        }
    }
}
\begin{document}
    \begin{figure}[htbp]
        \centering
        \begin{tikzpicture}[
            scale=0.5, 
            disk/.style={draw, thick, circle, fill=none},
            center/.style={draw,shape=rectangle,fill=blue},
            intersection/.style={draw, circle, fill=darkgray, inner sep=0.8mm}
            ]
            \node at (-6,0) {$A$};
            \node at (1,0) {$B$};
            \node at (-2,-6) {$C$};
            \draw[thick,transform shape,
            ] (-8,0) pic{carc=-100:50:60mm};
            \draw[thick,transform shape] (2,0) pic{carc=130:300:60mm};
            \draw[thick,red,transform shape] (3.2,0) pic{carc=130:300:60mm};
            \draw[thick,transform shape] (-2,-14) pic{carc=30:150:100mm};
            \draw[dashed] (-3,6) -- (-3,-6);
            \draw[red] (-2.8,6) -- (-2.8,-6);
            \draw[blue] (-2.2,6) -- (-2.2,-6);
        \end{tikzpicture}
        \caption{Zoomed in\label{fig:zoom}}
    \end{figure}
\end{document}

Answer 2

The pic is not scaled correctly. You should separately scale=0.5 in the carc definition

  \documentclass[a4paper]{article}
\usepackage{tikz}
\tikzset{
    pics/carc/.style args={#1:#2:#3}{
        code={
            \draw[pic actions,scale=0.5] (#1:#3) arc(#1:#2:#3);
        }
    }
}
\begin{document}


    \begin{figure}[htbp]
        \centering
        \begin{tikzpicture}[scale=0.5]
        \tikzstyle{disk} = [draw, thick, circle,fill=none]
        \tikzstyle{center} = [draw,shape=rectangle,fill=blue]
        \tikzstyle{intersection} = [draw, circle ,fill=darkgray, inner sep=0.8mm]
        \node at (-6,0) {$A$};
        \node at (1,0) {$B$};
        \node at (-2,-6) {$C$};
        \draw[thick] (-8,0)  pic{carc=-100:50:60mm};
        \draw[thick] (2,0)  pic{carc=130:300:60mm};
        \draw[thick,red] (3.2,0)  pic{carc=130:300:60mm};
        \draw[thick] (-2,-14)  pic{carc=30:150:100mm};
        \draw[dashed] (-3,6)--(-3, -6);
        \draw[red] (-2.8,6)--(-2.8, -6);
        \draw[blue] (-2.2,6)--(-2.2, -6);
        \end{tikzpicture}
        \caption{Zoomed in}
        \label{fig:zoom}
    \end{figure}

\end{document}