#!/bin/bash
#
#  slideshow_morph  images
#
# This program attempts to use the -remote capabilities of "animate" to
# generate a morphing slideshow on the fly.  That is while one picture is
# being displayed, the program will select (at random) and prepare the next
# morph or 'transition' to use.
#
# Note that all images given should be all the same size!
#
####
#

files=( "$@" )    # just save all the image filenames into an array

if [ ${#files} -le 1 ]; then
  echo >&2 "$0: 2 or more images needed to form a slideshow!"
fi

# Pick a random image from that list
#
prev_index=`expr $RANDOM \* ${#files} / 32768`
prev_image="${files[$prev_index]}"


# display it in background
animate -delay 100 "$prev_image" &
animate_pid=$!


# Set up a temporary for the transition animation with automatic cleanup
# MIFF format to hole transition animation (MIFF is better than GIF)
temp=/tmp/slideshow.$$.miff
trap "rm -f $temp; kill $animate_pid 2>/dev/null; exit 10" 1 2 3 15
trap "rm -f $temp; exit 0" 0


# Loop forwever
while :; do

  # pick next image
  next_index=`expr $RANDOM \* ${#files} / 32768`
  [ $next_index -eq $prev_index ] && continue   # try again
  next_image="${files[$next_index]}"

  # Do you complex image transition here
  # The final delay is minimum display time
  convert "$prev_image" "$next_image" -morph 10 \
          \( +clone -set delay 500 \) +swap +delete \
          $temp

  # Has the animation been killed! if so exit
  kill -0 $animate_pid || exit 0

  # feed transition to the animation
  animate -remote ephemeral:$temp &
  # wait for 'ephemeral:' file to have been read
  while [ -f $temp ]; do sleep .1; done
  # wait for transition time period to complete
  sleep 2
  # replace with just the new image
  animate -delay 100 -remote "$next_image" &

  # At this point we can now take as long as needed
  # to generate a new transition!

  prev_index=$next_index
  prev_image="$next_image"

done