[pstricks] opacity masks in pstricks

[mathias legrand]

Hi all,

I'm concerned with opacity masks such as, for instance:
http://www.designertoday.com/Tutorials/Illustrator/2399/Opacity.Mask.Adobe.Illustrator.CS.Tutorial.aspx

Will they be soon available in pstricks?
Today, I was unsuccessfully trying something like this:

\documentclass{article}
\usepackage[margin=0in]{geometry}
\usepackage{multido}
\usepackage{pstricks-add}
\begin{document}
\begin{figure}[h]
\centering%
\psset{unit=0.75}%
\def\xMax{12}%
\def\yMax{6}%
\begin{pspicture}(0,-\yMax)(\xMax,\yMax)%
\psclip{%
\multido{\i=0+1}{10}{%
\multido{\I=0+1}{20}{%
\rput[cc](! \i\space 2 mul \I\space 2 mul 28 sub){% 
\psframe[cornersize=absolute,linestyle=none,fillstyle=solid,fillcolor=black](-0.72,-0.72)(0.72,0.72)%
}}}}%
\multido{\i=0+1}{10}{%
\multido{\I=0+1}{20}{%
\rput[cc](! \i\space 2.5 mul \I\space 2.5 mul 28 sub){%
\pscircle[linestyle=none,fillstyle=solid,fillcolor=red](0,0){1}%
}}}%
\endpsclip
\end{pspicture}
\end{figure}
\end{document}