#!/bin/sh
#
# Create a animation of whirlpool sucking the image down the drain.
# An extra border is added then later removed to ensure whole image
# is sucked down into the center.
#
command='convert -delay 10 koala.gif'
command="$command -bordercolor lightblue -border 40x40"

for i in `seq 1 72`; do
  s_arg=`echo "$i * 15" | bc`
  i_arg=`echo "scale=2; $i / 54" | bc`
  command="$command \\( -clone 0 -swirl $s_arg -implode $i_arg \\)"
done

command="$command -shave 40x40 +repage -loop 0 animated_whirlpool.gif"

eval $command

chmod 644 animated_whirlpool.gif