#!/bin/ksh
#The command line argument is the name of a .jpg file.
#Cut out 9 squares of s x s pixels.
#http://netpbm.sourceforge.net/doc/

n=3
s=100	#length of side of square
PATH=/opt/sfw/netpbm/bin:$PATH

#width and height in pixels of $1.jpg
w=`jpegtopnm $1.jpg | pamfile | awk '{print $4}'`
h=`jpegtopnm $1.jpg | pamfile | awk '{print $6}'`

for row in 0 1 2
do
	for col in 0 1 2
	do

		rm -f $row$col.png
		jpegtopnm $1.jpg |
			pamcut \
			-left   $(((w - n * s) / 2 - 1 + s * col)) \
			-right  $(((w - n * s) / 2 - 1 + s * (col + 1) - 1)) \
			-top    $(((h - n * s) / 2 - 1 + s * row)) \
			-bottom $(((h - n * s) / 2 - 1 + s * (row + 1) - 1)) |
		pnmtopng > $row$col.png
		chmod 444 $row$col.png
	done
done

exit 0