根据包含的图形中心子图

Question

我的论文中有一张图，其中我包含一张图片，图片上有一堆标签，用于标识图片的不同方面，有些标签很长，有些标签很短。问题是其中一些标签很长，导致整个图像偏移，如下所示。 我想让图像本身（不包括我添加的标签）居中对齐。我该怎么做？

这是一个 MWE，与我在文档中所做的基本相同。

\documentclass[letterpaper]{article}

\usepackage{subcaption}
\usepackage{pgfplots}
\pgfplotsset{compat=newest}
\usepackage{tikz}
\usepackage{graphicx}

\begin{document}


\begin{figure}
\centering
\begin{subfigure}[b]{0.9\textwidth}
\begin{tikzpicture}
\node[anchor=south west,inner sep=0](image) at (0,0) {\includegraphics[width=0.35\textwidth]{example-image-a}};
\begin{scope}[x={(image.south east)},y={(image.north west)}]
    \node[anchor=east,align=right,draw=none] at (-0.10,0.80) {A loooooooooong label};
    \node[anchor=west,align=left ,draw=none] at ( 1.10,0.05) {Short Label};
    \draw[black,->,thick] (-0.10,0.80) -- (0.40,0.70);  %Outlet expansion line
    \draw[black,->,thick] ( 1.10,0.05) -- (0.30,0.10);  %Seeding array line
\end{scope}
\end{tikzpicture}
\caption{\label{subfig1}}
\end{subfigure}
\label{fig1}
\caption{An off-center figure}
\end{figure}

\end{document}

Answer 1

只需在相关的地方使用\rlap和\llap（\centering当然也要使图像本身居中）：

\documentclass[letterpaper]{article}

\usepackage{subcaption}
\usepackage{pgfplots}
\pgfplotsset{compat=newest}
\usepackage{tikz}
\usepackage{graphicx}

\begin{document}

\begin{figure}
  \centering
  \begin{subfigure}[b]{0.9\textwidth}
    \centering
    \begin{tikzpicture}
      \node[anchor=south west,inner sep=0](image) at (0,0) {\includegraphics[width=0.35\textwidth]{example-image-a}};
      \begin{scope}[x={(image.south east)},y={(image.north west)}]
        \node[anchor=east,align=right,draw=none] at (-0.10,0.80) {\llap{A loooooooooong label}};
        \node[anchor=west,align=left ,draw=none] at ( 1.10,0.05) {\rlap{Short Label}};
        \draw[black,->,thick] (-0.10,0.80) -- (0.40,0.70); %Outlet expansion line
        \draw[black,->,thick] ( 1.10,0.05) -- (0.30,0.10); %Seeding array line
      \end{scope}
    \end{tikzpicture}
    \caption{\label{subfig1}}
  \end{subfigure}
  \label{fig1}
  \caption{An off-center figure}
\end{figure}

\end{document} 

Answer 2

\centering在 的开头添加subfigure，然后\useasboundingbox (image.south east) rectangle (image.north west);在tikzpicture之前添加scope。这样 的边界框tikzpicture仅由图像的大小定义。

顺便说一下，pgfplots加载tikz，并tikz加载graphicx。因此，您实际上不必在 之后加载后两个\usepackage{pgfplots}。此外，建议使用 的特定版本compat，而不是compat=newest。这样做的原因是，如果pgfplots更新，即使代码没有改变，您的图的外观也可能会改变。

我刚刚意识到一件事：如果标签位于图像上方或下方，这种方法效果就不太好。可以使用以下方法手动修复此问题：\useasboundingbox ([yshift=-1cm]image.south east) rectangle ([yshift=1cm]image.north west);修改1cm和调整-1cm为有用的长度，具体取决于标签位置。从这个意义上说，Bernard 的答案更好。

\documentclass[letterpaper]{article}

\usepackage{subcaption}
\usepackage{pgfplots}
\pgfplotsset{compat=1.13}
\begin{document}


\begin{figure}
\centering
\begin{subfigure}[b]{0.9\textwidth}
\centering
\begin{tikzpicture}
\node[anchor=south west,inner sep=0](image) at (0,0) {\includegraphics[width=0.35\textwidth]{example-image-a}};
\useasboundingbox (image.south east) rectangle (image.north west);
\begin{scope}[x={(image.south east)},y={(image.north west)}]
    \node[anchor=east,align=right,draw=none] at (-0.10,0.80) {A loooooooooong label};
    \node[anchor=west,align=left ,draw=none] at ( 1.10,0.05) {Short Label};
    \draw[black,->,thick] (-0.10,0.80) -- (0.40,0.70);  %Outlet expansion line
    \draw[black,->,thick] ( 1.10,0.05) -- (0.30,0.10);  %Seeding array line
\end{scope}
\end{tikzpicture}
\caption{\label{subfig1}}
\end{subfigure}
\label{fig1}
\caption{An off-center figure}
\end{figure}

\end{document}