Floats wider than text in Latex

Latex floats by default have the text width or smaller. Took me some time to figure out how to make a float wider than the text width itself. Here is an example how it is possible to do it, with pretty simple setup and no custom packages. Just note the custom command defined:

\documentclass{article}
\usepackage{changepage}
\usepackage{graphicx}
\usepackage{float}
\usepackage{lipsum}% just to automatically generate some text
\newenvironment{changemargin}[2]{\begin{list}{}{
\setlength{\topsep}{0pt}\setlength{\leftmargin}{0pt}
 \setlength{\rightmargin}{0pt}
 \setlength{\listparindent}{\parindent}
 \setlength{\itemindent}{\parindent}
 \setlength{\parsep}{0pt plus 1pt}
 \addtolength{\leftmargin}{#1}\addtolength{\rightmargin}{#2}
 }\item }{\end{list}}

\begin{document}

\lipsum[1-2]

\begin{figure}[t]
\begin{changemargin}{-3cm}{2cm}
 \lipsum[1]
 \includegraphics[scale=0.3]{./pics/co3-2gim-reaction.png}
\end{changemargin}
\caption{asdfasdf}
\end{figure}

\lipsum[1-5]

\end{document}