Great! Thanks Hans, now it works. I replaced the "draw externalfigure"
commands by

draw externalfigure "./skysprite.png" xsized 4u ysized 5u shifted (0u,-0u);
draw externalfigure "./sandsprite.png" xsized 4u ysized 5u shifted (0u,-5u);

Best regards

On Sun, Jan 2, 2022 at 3:36 PM Hans Hagen <j.hagen@xs4all.nl> wrote:

> On 1/2/2022 3:12 PM, Alfredo Catalina via ntg-context wrote:
> > I'm trying to use ConTeXt with Metafun to produce a map of a videogame I
> > am working on. In fact I did it 9 years ago but it seems that now it
> > doesn't work.
> >
> > I have two 32 pixels wide by 40 pixels high sprites. They are saved in
> > the skysprite.png and sandsprite.png files. Since 32 = 4 x 8 and 40 = 5
> > x 8, the width/height ratio is 4/5.
> >
> > This should produce a page with a sky sprite and a sand sprite, one
> > below the other. It worked in the past. Each sprite should be 4 x 0.095
> > cm = 0,38 cm wide and 5 x 0.095 cm = 0.475 cm high:
> >
> > \starttext
> > \setupMPinstance[metafun][textstyle={\switchtobodyfont[termes,8pt]}]
> > \startuseMPgraphic{mapa}
> > u:=.095cm;
> > draw externalfigure "./skysprite.png" xscaled 4u yscaled 5u shifted
> > (0u,-0u);
> > draw externalfigure "./sandsprite.png" xscaled 4u yscaled 5u shifted
> > (0u,-5u);
> > \stopuseMPgraphic
> > \useMPgraphic{mapa}
> > \stoptext
> >
> > But instead I got two huge sprites of 2.8 cm x 4.4 cm.
> >
> > Am I forgetting something?
> Originally that worked because the image was always 'included' at 1 bp
> and then scaled but that was (1) inaccurate and (2) a bit depending on
> the image and (3) could overflow metapost.
>
> Use xsized and ysized instead (absolute measures instead of scaling the
> unknown)
>
> Hans
>
> -----------------------------------------------------------------
>                                            Hans Hagen | PRAGMA ADE
>                Ridderstraat 27 | 8061 GH Hasselt | The Netherlands
>         tel: 038 477 53 69 | www.pragma-ade.nl | www.pragma-pod.nl
> -----------------------------------------------------------------
>