z=(
close
dilate
erode
open
)
g=2;
echo $g > ../test/g.txt

for x in *jpg;do
for j in ${z[@]};do
for i in {2,5,8,16};do
#echo $j $i
#echo $x ../test/${x%.*}-c$i-$j$g.jpg;
convert +dither -colors $i -depth 4 -morphology "${j}" octagon:$g $x ../test/${x%.*}-c$i-$j$g.jpg;
done;done;done

ls *-c2-*2.jpg|wc -l
for i in {2,5,8,16};do
ls *-c$i-*2.jpg|sort -t- -k3 > testlist;montage @testlist -tile 9x -geometry +2+2 x-c$i.jpeg;
#ls *-c$i-*2.jpg|sort > testlist;montage @testlist -tile x9 -geometry +2+2 x-c$i.jpeg;
done

###ls ../test/| sort -s -t"-" -k3 -k2.2n > ../test/testlist
g=$(cat g.txt);ls *jpg| sort -s -t"-" -k3 -k2.2n > testlist;montage @testlist -geometry +2+2 $x$g.jpeg;rm *jpg


#mark, moutain, laptop
for x in *.jpg;do 
convert +dither -colors 3 -depth 4 -morphology open octagon:1 $x ../test/${x%.*}-2.jpg;
done 
ls *-2.jpg|sort > testlist; montage @testlist -geometry +2+2 xxx.jpeg

for i in {2..5};do
convert +dither -colors $i -depth 4 -morphology open octagon:1 $x ${x%.*}-$i.jpg;
done


seems about right value:
c8 close1
c2 dilate1
c2 c5 open close Octagon:2 or 1
posterize:
c16 open close Octagon:2