Apple hates its own history.
In newer versions of its os, pict format is poorly supported. (e.g. Preview cannot open pict files as it usually did ), solution here:
Install Imagemagick and use it’s convert function to convert.
in it’s simpliest form “convert source.pict dest.jpg”
to process a batch of files in a dir:
for f in *.pct; do convert “$f” “${f%.*}.png”; done
