[pstricks] fill around image

[Henry Proudhon]

Hi everone,

I'm trying to make a figure, in which I'd like to include an image with 
a transparent background.
The image should be superimposed to a pstricks fillstyle says 
fillstyle=vlines.

pb: when I convert the image to include as eps, I loose transparency of 
course. I cannot draw over the image because the contour is too much 
complicated...

I don't see any solution here... :-(

Here is a minimal example:

\documentclass{article}

\usepackage{pstricks}
\usepackage{graphicx}
\pagestyle{empty}
\begin{document}
    \psset{xunit=1cm,yunit=1cm}
    \begin{pspicture}(-7,-5)(7,5)
         \psframe[%
    linestyle=none,%
    fillstyle=vlines,%
    hatchcolor=lightgray,%
    hatchsep=0.5pt%
    ](-2,-2)(2,2)
        
\rput(0.0,0.0){\includegraphics[width=4cm]{image_with_transparent_background.eps}}
    \end{pspicture}
\end{document}

Any idea ? thanks

Henry