\documentclass[12pt]{article}

\def\showgraph{%
  \par\medskip\centerline{\raise 1em\box\graph}\bigskip\noindent\ignorespaces}

\begin{document}

\verb"gpic -t test_gpic.pic > test_gpic.tex"

Here is the picture:

.PS
Z: box invis ht 4.2 wid 1.2 fill 0.05
A: box ht 4 wid 1 fill 0.1 at Z
B: box ht 1 wid 0.5 fill 0.2 at A + (0, -1)
C: box ht 1 wid 0.5 fill 0.4 at A + (0, 1)
D: box invis ht 0.25 wid 0.5 fill 0.0 at A + (0, 0)
.PE

\centerline{\raise 1em\box\graph}

\end{document}
