captionsfloats
How can I set the width of the caption to be the same as the width of the pic when I give a height of a picture and have the width deduced automatically by aspect ratio?
\begin{figure}
\includegraphics[height=10cm]{pic.png}
\caption{My very long caption ....}
\end{figure}
In this case the pic is on the left (let's assume only 12cm wide) and the caption is running over the complete text width.
The default definition of \caption in article and the other standard classes is not boxed if the caption is more than a line. To change the effective line width you should use quote (or an environment with similar definition) which is
\newenvironment{quote}
{\list{}{\rightmargin\leftmargin}%
\item\relax}
{\endlist}
Which just accepts the default increase of \leftmargin and makes \rightmargin the same. You can set the two margins explicitly to any appropriate value in the definition of a custom environment to wrap the caption
\begin{center}
\includegraphics
\nopagebreak
\begin{quote}
\captionof{figure}{looooong caption}
\end{quote}
\end{center}
Using the subcaption package, I could make the following.
This is the code I used to generate that (admittedly, I didn't have the llncs package installed, so I changed that out for article).
\documentclass{article}
\usepackage{todonotes}
\usepackage{floatflt}
\usepackage{graphicx}
\usepackage{subcaption}
\begin{document}
\begin{figure}[t!]
\centering
\begin{subfigure}[t]{0.47\textwidth}
\centering
\missingfigure[figwidth=\textwidth]{Testing a long text string}
\caption{Resource Owner Password \\ Credential Grant}
\label{fig:pwd_grant}
\end{subfigure}\hfill
\begin{subfigure}[t]{0.47\textwidth}
\centering
\missingfigure[figwidth=\textwidth]{Testing a long text string}
\caption{Client Credential Grant}
\label{fig:client_grant}
\end{subfigure}
\caption{grants}
\label{fig:auth_impl_grant}
\end{figure}
\end{document}
Do note however that subcaption and subfig are not compatible! For what it's worth though, subfig was getting pretty obsolete last time I checked, while subcaption fixes some of its flaws (compatibility with hyperref being a big one).
After some more work, OP went with the following code.
\documentclass{llncs}
\usepackage{todonotes}
\usepackage{floatflt}
\usepackage{graphicx}
\usepackage{subcaption}
\captionsetup{compatibility=false}
\begin{document}
\begin{figure}[t!]
\makebox[\linewidth][c]{
\subcaptionbox{Resource Owner Password\\ Credential Grant}[.47\linewidth]{
\missingfigure[figwidth=\textwidth]{Testing a text string}
\label{fig:auth_grant}
}
\hspace*{2cm}
\subcaptionbox{Client Credential Grant}[.47\linewidth]{
\centering
\missingfigure[figwidth=\textwidth]{Testing a text string}
\label{fig:impl_grant}
}
}
\caption{Caption}
\label{fig:auth_impl_grant}
\end{figure}
\end{document}
Best Answer
You need to store the image in a savebox and then wrap the caption into a minipage with the width of the box.
The
adjustboxpackage simplifies this approach and also avoids "bad box" warnings if the image is larger then the usual text width.