\documentclass[a4paper,12pt]{report}
\usepackage[abs]{overpic}
\begin{document}

\begin{overpic}[unit=1pt,grid,tics=20]{rgray.eps}
\put(100,100){\makebox(0,0)[l]{rechts oben}}
\put(50,50){\makebox(0,0){Mitte}}
\put(0,0){\makebox(0,0)[tr]{links unten}}
\end{overpic}


\end{document}