Re: metapost question

["Wolfgang Schuster" <schuster.wolfgang@googlemail.com>]

On Wed, Jun 18, 2008 at 1:14 PM, Thomas A. Schmitz
<thomas.schmitz@uni-bonn.de> wrote:
> Hi all,
>
> probably an easy question: for a presentation, I would like to have an
> area of my slide highlighted by placing a transparent grey layer on
> top of the slide and having one area of this layer completely
> transparent, a bit like this screenshot: http://debaday.debian.net/wp-content/uploads/2007/05/key3.jpg
> Any suggestions for the easiest way to achieve this effect?

\setupexternalfigures[location={local,global,default}]

\definecolor[tgray][r=.8,t=.5,a=1]

\startuseMPgraphic{highlighted}
path p, q ;
p = unitsquare xyscaled(OverlayWidth,OverlayHeight) ;
q= fullcircle scaled 3cm shifted (12cm,10cm) ;
fill p--reverse q--cycle withcolor \MPcolor{tgray} ;
\stopuseMPgraphic

\defineoverlay[image][\overlayfigure{hacker}]
\defineoverlay[shade][\useMPgraphic{highlighted}]

\setupbackgrounds[page][background={image,shade}]

\setuppapersize[S6][S6]

\starttext
\page[empty]
\stoptext

Wolfgang
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