我正在处理一个文档，其中有几张图并排放置。其中一些使用“填充”，而另一些则不使用。现在的问题是，根据是否使用此功能，图例的字体大小会有所不同。此外，图的厚度也会受到影响。作为一种解决方法，我现在在每个图中都使用一个空的“填充”（第三个 tikzpicture），但这感觉太像作弊了，我很想知道这里到底发生了什么。
以下是 MWE：
\documentclass{article}
\usepackage{pgfplots}
\pgfplotsset{compat=1.13}
\usepgfplotslibrary{fillbetween}
\begin{document}
\begin{tikzpicture}[scale=0.55]
\begin{axis}[
ticks=none, axis x line* = bottom,
samples= 160, domain = -3:3,
xmin = -3, xmax = 3,
ymin = 0, ymax = 3,
legend style={at={(axis cs:2.9,2.9)},anchor=north east}]
\addplot[name path=f, black, thick, mark=none, ] {max(2.8-2*x^2,0)};
\addplot[name path=g, black, thick, mark=none, dashed, ] {max(1-0.3*x^2,0)};
\addplot[name path=line, gray, no markers, line width=0pt] {0};
\addplot[color=gray, fill opacity=0.25] fill between[of = f and line, split];
\legend{$f$,$q$}
\end{axis}
\end{tikzpicture}\hspace{5em}
\begin{tikzpicture}[scale=0.55]
\begin{axis}[
ticks=none, axis x line* = bottom,
samples= 160, domain = -3:3,
xmin = -3, xmax = 3,
ymin = 0, ymax = 3,
legend style={at={(axis cs:2.9,2.9)},anchor=north east}]
\addplot[name path=f, black, thick, mark=none, ] {max(2.8-2*x^2,0)};
\addplot[name path=g, black, thick, mark=none, dashed, ] {max(1-0.3*x^2,0)};
\addplot[name path=line, gray, no markers, line width=0pt] {0};
\legend{$f$,$q$}
\end{axis}
\end{tikzpicture}
\begin{tikzpicture}[scale=0.55]
\begin{axis}[
ticks=none, axis x line* = bottom,
samples= 160, domain = -3:3,
xmin = -3, xmax = 3,
ymin = 0, ymax = 3,
legend style={at={(axis cs:2.9,2.9)},anchor=north east}]
\addplot[name path=f, black, thick, mark=none, ] {max(2.8-2*x^2,0)};
\addplot[name path=g, black, thick, mark=none, dashed, ] {max(1-0.3*x^2,0)};
\addplot[name path=line, gray, no markers, line width=0pt] {0};
\addplot[color=gray, fill opacity=0.25] fill between[of = line and line, split];
\legend{$f$,$q$}
\end{axis}
\end{tikzpicture}
\end{document}
编辑：感谢 Zarko 的回答，我现在认为这个问题是pgfplots 中 fillbetween 的缩放问题。出于某种原因，调用 fillbetween 会导致缩放突然影响图例。但我还没弄清楚为什么。
答案1
观察到的问题的原因是 TikZ 图片的缩放。如果省略，图例中的字体将不会改变。这让我想到fillbetween库的使用不允许缩放，即使缩放按预期工作：它不应该改变字体大小（据我了解它的工作原理，也许我错了）。
我在你的 MWE 中做了一些改变：省略缩放，引入图像宽度，并且它可以按预期工作：
\documentclass{article}
\usepackage{pgfplots}
\pgfplotsset{compat=1.13}
\usepgfplotslibrary{fillbetween}
\usepackage{showframe}
\begin{document}
\noindent%
\begin{tikzpicture}
\begin{axis}[
width=0.45\textwidth,
ticks=none, axis x line* = bottom,
samples= 160, domain = -3:3,
xmin = -3, xmax = 3,
ymin = 0, ymax = 3,
legend style={at={(0.97,0.99)}, anchor=north east},
]
\addplot[name path=f, black, thick, mark=none, ] {max(2.8-2*x^2,0)};
\addplot[name path=g, black, thick, mark=none, dashed, ] {max(1-0.3*x^2,0)};
\addplot[name path=line, gray, no markers, line width=0pt] {0};
\addplot[color=gray, fill opacity=0.25] fill between[of = f and line, split];
\legend{$f$,$q$}
\end{axis}
\end{tikzpicture}\hfill
\begin{tikzpicture}
\begin{axis}[
width=0.45\textwidth,
ticks=none, axis x line* = bottom,
samples= 160, domain = -3:3,
xmin = -3, xmax = 3,
ymin = 0, ymax = 3,
legend style={at={(0.97,0.99)}, anchor=north east},
]
\addplot[name path=f, black, thick, mark=none, ] {max(2.8-2*x^2,0)};
\addplot[name path=g, black, thick, mark=none, dashed, ] {max(1-0.3*x^2,0)};
\addplot[name path=line, gray, no markers, line width=0pt] {0};
\legend{$f$,$q$}
\end{axis}
\end{tikzpicture}\hfill
\begin{tikzpicture}
\begin{axis}[
width=0.45\textwidth,
ticks=none, axis x line* = bottom,
samples= 160, domain = -3:3,
xmin = -3, xmax = 3,
ymin = 0, ymax = 3,
legend style={at={(0.97,0.99)}, anchor=north east},
]
\addplot[name path=f, black, thick, mark=none, ] {max(2.8-2*x^2,0)};
\addplot[name path=g, black, thick, mark=none, dashed, ] {max(1-0.3*x^2,0)};
\addplot[name path=line, gray, no markers, line width=0pt] {0};
\addplot[color=gray, fill opacity=0.25] fill between[of = f and line, split];
\legend{$f$,$q$}
\end{axis}
\end{tikzpicture}
\end{document}
