Background color for existing floats (e.g. w/o defining a new environment)?

Question

I'm trying to make all my figures (including caption) backgrounded with a decent color.

I already found these questions with some nice answers:

• How to set a background color of figure environment?
• Rounded corner colored box around figure
• Background color boxes around complete figure in LaTeX

But all these answers have in common that they define some new environments or commands that need to be put inside the figures or replace the figures completly.

Is there a way to put a background color behind existing floats without having to change the content of these existing floats?

Answer 1

\documentclass{article}

\makeatletter

\def\foo#1\normalcolor\vbox\bgroup#2!!{%
\def\@xfloat ##1[##2]{#1%
 \normalcolor
      \hbox\bgroup{\color{yellow}\leaders\vrule\hskip\columnwidth\hskip-\columnwidth}%
      \vbox \bgroup\aftergroup\egroup
#2}}
\expandafter\foo\@xfloat{#1}[#2]!!

\makeatother

\usepackage{color}
\begin{document}

\begin{figure}
a\\b\\c
\caption{yes no}
\end{figure}

one two three

\end{document}

Answer 2

Here is an elementary implementation using mdframed that redefines the figure environment (therefore not adapting the usage of figure in your document):

\documentclass{article}
\usepackage{lipsum,mdframed,xcolor}% http://ctan.org/pkg/{lipsum,mdframed,xcolor}
\let\oldfigure\figure% Store old figure environment start
\let\endoldfigure\endfigure% Store old figure environment end
\renewenvironment{figure}[1][htbp]% Redefine figure
  {\oldfigure[#1]\mdframed[backgroundcolor=blue!15]}
  {\endmdframed\endoldfigure}
\begin{document}
\lipsum[1]
\begin{figure}[ht]
  \centering\includegraphics{example-image-a}
  \caption{This is a figure}
\end{figure}
\lipsum[2]
\end{document}

From here it would be straight forward to apply a different style to a different float (like table, for example).