Incremental graphics with texpower?

I'm preparing a presentation with multiply used big jpeg
pictures. in each slide another overlay is positioned on the
picture to highliht or explain something.
I've managed to build the "incremental" graphics with XFig
using the layers (eg. "base figure" occupies layers 100-50, and the overlays
occupies layers 40,39,38,...; then I export the particular figures with:
fig2dev -Lpdf -D+50:100 tcd.fig > tcd.pdf #(for base figure)
fig2dev -Lpdf -D+40 tcd.fig > tcd.pdf #(for first overlay)

I can display the picture with the overlay using code like this (based on:
http://www.educat.hu-berlin.de/~voss/lyx/LaTeX/overwrite.phtml)

********************* BEGIN *************************
\documentclass[12pt]{article}
\usepackage[screen,nopanel,sectionbreak]{pdfscreen}
\margins{2ex}{2ex}{2ex}{2ex}
\screensize{6.25in}{8in}
\usepackage[display]{texpower}
\usepackage{tpslifonts}
\usepackage{graphicx}

\newsavebox{\ImageBox}
\begin{document}

\section{A picture}
\pdfximage{tcd.pdf}
\savebox{\ImageBox}{\pdfrefximage\pdflastximage}
\begin{center}%
\makeatletter
\newcommand\wdWithoutUnit{\wd\ImageBox\@gobble}
\newcommand\htWithoutUnit{\ht\ImageBox\@gobble}
\makeatother
\begin{picture}(\wdWithoutUnit,\htWithoutUnit)
\setlength{\unitlength}{1cm}
\linethickness{1pt}
\put(0,0){\usebox{\ImageBox}}
\put(0,0){\pdfximage{tcd1.pdf}\pdfrefximage\pdflastximage}
\end{picture}
\end{center}%
\end{document}
********************* END *************************

However, I would like to build my graphics incrementally using the code like
this (DOESN'T WORK :-( because stepwise can not be used in the picture
environment)

********************* BEGIN *************************
\documentclass[12pt]{article}
\usepackage[screen,nopanel,sectionbreak]{pdfscreen}
\margins{2ex}{2ex}{2ex}{2ex}
\screensize{6.25in}{8in}
\usepackage[display]{texpower}
\usepackage{tpslifonts}
\usepackage{graphicx}

\newsavebox{\ImageBox}
\begin{document}

\section{A picture}
\pdfximage{tcd.pdf}
\savebox{\ImageBox}{\pdfrefximage\pdflastximage}
\begin{center}%
\makeatletter
\newcommand\wdWithoutUnit{\wd\ImageBox\@gobble}
\newcommand\htWithoutUnit{\ht\ImageBox\@gobble}
\makeatother
\begin{picture}(\wdWithoutUnit,\htWithoutUnit)
\setlength{\unitlength}{1cm}
\linethickness{1pt}
\put(0,0){\usebox{\ImageBox}}
\stepwise{
\step{\put(0,0){\pdfximage{tcd1.pdf}\pdfrefximage\pdflastximage}}
\step{\put(0,0){\pdfximage{tcd2.pdf}\pdfrefximage\pdflastximage}}
\step{\put(0,0){\pdfximage{tcd3.pdf}\pdfrefximage\pdflastximage}}
}
\end{picture}
\end{center}%
\end{document}
********************* END *************************
Is it any good way to obtain the expected "incremental" graphics?
Additionally it would be good to have the functions available in the prosper
package:
\fromSlide, \onlySlide, \untilSlide and so on....
Is it possible to emulate them?
-- 
Thanks in advance,
Best regards
Wojtek Zabolotny
[email protected] 


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