find . -name "*.ppm" | while read line
do ts=$(echo $line | awk -F . '{print $3}')
rt=$(expr $ts \* 1)
rt="${rt} fs"
echo $rt
convert -font helvetica -fill white -pointsize 36 -draw "text 80,50 '$rt'" $line foo.$ts.jpg
done

mkdir img_seq
mv *.jpg ./img_seq/