Subfloat: How to align subcaption of image to same elevation as other subcaption?

Question

Assumed we have two images with different heights. Both images are aligned to the top via valign=t.

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Minimum working example (MWE):

\documentclass{article}
\usepackage{subfig}
\usepackage[export]{adjustbox}

\begin{document}

\begin{figure}[h]
    \centering
    \subfloat[This is image A]{\includegraphics[width=0.45\textwidth, valign=t]{example-image-16x10}}\qquad
    \subfloat[This is image B]{\includegraphics[width=0.45\textwidth, valign=t]{example-image-10x16}}\\
    \caption{Caption for images A and B}
\end{figure}

\end{document}

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Screenshot of the result:

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Description of the issue:

Unfortunately the corresponding caption also moves up to the top with this command.

While both images should remain at the top, the left image caption should move down to the red dashed elevation line of the other caption for better appearance.

How to do so?

Answer 1

Alignment generally involves using baselines, but in this case you need to add a gap between the image and the caption. You will also need to compute the difference between the heights of the two images.

\documentclass{article}
\usepackage{subcaption}
\usepackage{graphicx}

\begin{document}

\begin{figure}[htp]
    \centering
    \sbox0{\includegraphics[width=0.45\textwidth]{example-image-16x10}}% measure image
    \sbox1{\includegraphics[width=0.45\textwidth]{example-image-10x16}}% measure image
    \begin{subfigure}{\wd0}
      \usebox0%
      \vspace{\dimexpr \ht1-\ht0}% fill space
      \caption{This is image A}
    \end{subfigure}\qquad% I prefer \hfil
    \begin{subfigure}{\wd1}
      \usebox1
      \caption{This is image B}
    \end{subfigure}
    \caption{Caption for images A and B}
\end{figure}

\end{document}

Answer 2

floatrow is recommended by Overleaf "for advanced caption managing of floating elements (tables and figures)".

It requires changing the environment a bit, but don't be put off by the apparent added complexity because it works very well.

Example:

\documentclass{article}
\usepackage{subcaption}
\usepackage{graphicx}
\usepackage{floatrow}
\begin{document}
\begin{figure}[h!]
    \centering
    \floatsetup{heightadjust=all, valign=t}
    \ffigbox{
        \begin{subfloatrow}
            \ffigbox[\FBwidth]{
                {\includegraphics[width=0.45\textwidth]{example-image-16x10}}
                {\caption{This is image A}
            }
            \ffigbox[\FBwidth]{
                {\includegraphics[width=0.45\textwidth]{example-image-10x16}}
                {\caption{This is image B}
            }
        \end{subfloatrow}
    }
    {\caption{Caption for images A and B}}
\end{figure}
\end{document}

Some features of this method:

• You can swap valign=t for valign=c if you want the images vertically centred
• The subcaptions will be centred on the relevant image, thanks to \FBwidth. If the subcaptions are longer than the image width, they'll wrap

Answer 3

A solution with minipages and subcaption package:

\documentclass{article}
\usepackage{graphicx}
\usepackage{subcaption}
\usepackage[export]{adjustbox}
\usepackage{lipsum}

\begin{document}
\lipsum[1]    
\begin{figure}[h]
    \centering
    \begin{minipage}[t]{0.45\textwidth}
    \centering
    \includegraphics[width=\textwidth, valign=t]{example-image-16x10}
    \end{minipage}\hspace{\fill}
    \begin{minipage}[t]{0.45\textwidth}
    \centering
    \includegraphics[width=\textwidth, valign=t]{example-image-10x16}
    \end{minipage}
    \begin{minipage}[t]{0.45\textwidth}
    \captionof{subfigure}{This is image A}
    \end{minipage}\hspace{\fill}
    \begin{minipage}[t]{0.45\textwidth}
    \captionof{subfigure}{This is image B}
    \end{minipage}
    \caption{Caption for images A and B}
\end{figure}

\end{document}

Edit: Adding parentheses in subcaptions' label and a vertical space between images and captions:

\documentclass{article}
\usepackage{graphicx}
\usepackage{subcaption}
\captionsetup[subfigure]{labelformat = parens}
\usepackage[export]{adjustbox}
\usepackage{lipsum}

\begin{document}
\lipsum[1]    
\begin{figure}[h]
    \centering
    \begin{minipage}[t]{0.45\textwidth}
    \centering
    \includegraphics[width=\textwidth, valign=t]{example-image-16x10}
    \end{minipage}\hspace{\fill}
    \begin{minipage}[t]{0.45\textwidth}
    \centering
    \includegraphics[width=\textwidth, valign=t]{example-image-10x16}
    \end{minipage}
    \vspace{5pt}

    \begin{minipage}[t]{0.45\textwidth}
    \captionof{subfigure}{This is image A}
    \end{minipage}\hspace{\fill}
    \begin{minipage}[t]{0.45\textwidth}
    \captionof{subfigure}{This is image B}
    \end{minipage}
    \caption{Caption for images A and B}
\end{figure}

\end{document}