imgdiff

#!/bin/zsh

OLD="$2"
NEW="$5"

# "xc:none" ist "Nichts", entspricht einem fehlenden Bild
[ "$OLD" = "/dev/null" ] && OLD="xc:none"
[ "$NEW" = "/dev/null" ] && NEW="xc:none"

exec convert "$OLD" "$NEW" -alpha off \
    \( -clone 0-1 -compose difference -composite -threshold 0 \) \
    \( -clone 1-2 -compose copy_opacity -composite \
       -compose over -background white -flatten \) \
    -delete 2 -swap 1,2 +append \
    -background white -flatten x: