Wolfgang Schuster wrote:
> Hi,
>
> I make a hole in a MetaPost graphic and add a graphic as background but
> in MkIV I get no hole but the lines I try to remove are still visible.
>
> All files with the two results from MkII (what I want) and MkIV are in
> the attachment.
>
> \starttext
>
> \startMPcode
>
> picture temp ;
> path mask ;
>
> draw (0,1cm)--(2cm,1cm) ;
> draw (1cm,0)--(1cm,2cm) ;
>
> temp := currentpicture ;
> currentpicture := nullpicture ;
> mask := unitsquare scaled 2cm -- reverse fullsquare scaled 1cm shifted
> (1cm,1cm) -- cycle ;
> clip temp to mask ;
> currentpicture := temp ;
> draw fullsquare scaled 5mm shifted (1cm,1cm) ;
>
> temp := currentpicture ;
> currentpicture := nullpicture ;
> externalfigure "holz280.jpg" scaled 2cm ;
> addto currentpicture also temp ;
>
> \stopMPcode
>
> \stoptext

i have no clue (nor time to look into it in detail) but this seems to
work ok:

% engine=luatex interface=en

\starttext

\startMPpage
    externalfigure "cow.pdf" scaled 2cm ;
    clip currentpicture to boundingbox currentpicture -- reverse
unitsquare scaled 1cm shifted (.5cm,.5cm) -- cycle ;
\stopMPpage

\stoptext