为多列图形添加标题

Question

我需要为以下三幅图像添加标题：

我通过添加命令完成了此操作，caption如下面的代码片段所示，但它不起作用：

\begin{figure*}[ht]
\begin{center}
$\begin{array}{rl}
    \includegraphics[width=0.45\textwidth]{images/chapter4/img_1.png}\caption{Training set} &
    \includegraphics[width=0.45\textwidth]{images/chapter4/img_2.png}\caption{Validation set}\\
    \multicolumn{2}{c}{\includegraphics[width=0.45\textwidth]{images/chapter4/img_3.png.png}\caption{Test set}}
\end{array}$
\caption{Overall caption.}
\end{center}
\end{figure*}

我只看到整体的标题，但我还需要每张图片下方的标题。

Answer 1

最好使用子图：

\documentclass[12pt,a4paper]{article}

\usepackage{graphicx}

\usepackage[position=top]{subfig}% needed <<<<<<<<<<

\begin{document}
    
     \begin{figure*}[hp!]
        \centering
        \subfloat[Training set]{%       
            \includegraphics[width=0.45\textwidth]{example-image}
        }\hfill        
        \subfloat[Validation set]{%
            \includegraphics[width=0.45\textwidth]{example-image}
        }\\         
        \subfloat[Test set]{%
            \includegraphics[width=0.45\textwidth]{example-image}               
        }
        \caption{Overall caption.}
        \label{fig:images}
    \end{figure*} 

    See the used sets  in the figure \ref{fig:images}.

        
\end{document}

Answer 2

这是一个使用该floatrow软件包的简单解决方案：

\documentclass[twocolumn]{article}

\usepackage[draft]{graphicx}
\usepackage{caption, floatrow}
\DeclareCaptionSubType[alph]{figure}

\begin{document}

\begin{figure*}[!ht]
\ffigbox{\centering
\begin{subfloatrow}[2]
    \ffigbox{\includegraphics[width=0.45\textwidth]{images/chapter4/img_1.png}}{\caption{Training set}\label{TS}}
    \ffigbox{\includegraphics[width=0.45\textwidth]{images/chapter4/img_2.png}}{\caption{Validation set}\label{VS}}
\end{subfloatrow}
\vskip 4ex
\begin{subfloatrow}[1]
   \ffigbox{\includegraphics[width=0.45\textwidth]{images/chapter4/img_3.png.png}}{\caption{Test set}\label{TS}}
\end{subfloatrow}}
{\caption{Overall caption.}\label{OC}}
\end{figure*}

\end{document}