Vertically fit a figure with caption to page

Question

I have a very large(heightwise) figure and would like to fit it on a page with its caption, that I place below (document wide style which I would like to keep, and the figure fills the line anyhow, so placing the caption on the side is not a solution). Is there any way to scale the figure to fit the page with the caption? (I amaware of scalebox, but I would like to avoid scaling the captiontext).

\documentclass{report}
\usepackage{floatrow}
\usepackage[demo]{graphicx}
\floatsetup{style=ruled, footposition=caption, capposition=bottom, heightadjust=object}
\begin{document}
\begin{figure}
  \includegraphics[height=1.2\textheight]{dummy}
  \caption{this should be in text}
\end{figure}
\end{document}

Answer 1

You could work out how much space is taken up by your float style and adjust accordingly, or you could just let latex do it for you.

If you use

  \includegraphics[height=\dimexpr\textheight\relax]{dummy}

LaTeX reports

LaTeX Warning: Float too large for page by 22.2pt on input line 9.

so if you use

  \includegraphics[height=\dimexpr\textheight-22.2pt\relax]{dummy}

It is happy.

Answer 2

Use LaTeX to calculate the height automatically, and scale the image appropriately:

\documentclass{report}
\usepackage{floatrow}
\usepackage[demo]{graphicx}
\usepackage{calc}
\usepackage{fp}
\floatsetup{style=ruled, footposition=caption, capposition=bottom, heightadjust=object}
\begin{document}
\begin{figure}
  \newlength{\spacearoundfigures}        % It should be possible to calculate this value
  \setlength{\spacearoundfigures}{124pt} % Include \abovecaptionskip and \belowcaptionskip\
  \newsavebox{\figurebox}
  \savebox{\figurebox}{\includegraphics[height=1.2\textheight]{dummy}}
  \newsavebox{\captionbox}
  \savebox{\captionbox}{this should be in text}% N.B. only works for one-line captions add code to allow line breaking and limit width to \textwidth less figure horizontal space
  \newlength{\cbh}
  \settototalheight{\cbh}{\usebox{\captionbox}}
  \newlength{\fbh}
  \setlength{\fbh}{\textheight}
  \addtolength{\fbh}{-\cbh}
  \makeatletter\FPdiv\result{\strip@pt\fbh}{\strip@pt\textheight}\makeatother
  \scalebox{\result}{\usebox{\figurebox}}
  \caption{\usebox{\captionbox}}
\end{figure}
\end{document}