#!/bin/sh

# Barry Kauler 2011 GPL3 (/usr/share/doc/legal)

#pngoverlay.sh is an alternative to pngoverlay written by vovchik (in BaCon)

# (vovchik's pngoverlay requires X to be running, which may be a disadvantage)

#requires netpbm svn rev 1543 or later, with pamcomp -mixtransparency

#requires three params, 1st and 2nd must exist:

# bottom-image top-image output-image

#overlays the two images, with common areas of transparency in output image.



[ ! $3 ] && exit 1

[ ! -e "$1" ] && exit 1

[ ! -e "$2" ] && exit 1

[ "`echo -n "$1" | grep 'png$'`" = "" ] && exit 1

[ "`echo -n "$2" | grep 'png$'`" = "" ] && exit 1



pngtopam -alphapam "${1}" > /tmp/pngoverlay_${$}_1.pam

pngtopam -alphapam "${2}" > /tmp/pngoverlay_${$}_2.pam

#1st image on top, 2nd on bottom, 3rd is output...

pamcomp -mixtransparency /tmp/pngoverlay_${$}_2.pam /tmp/pngoverlay_${$}_1.pam > /tmp/pngoverlay_${$}_out.png 2> /dev/null

pamrgbatopng /tmp/pngoverlay_${$}_out.png > "${3}"

rm -f /tmp/pngoverlay_${$}_1.pam

rm -f /tmp/pngoverlay_${$}_2.pam

rm -f /tmp/pngoverlay_${$}_out.pam