#!/bin/bash
#
#  slideshow_next  image
#
# This program assumes an image is currently being displayed by the IM
# "animate" command. The image currently displayed is stored in the
# file "last_image" in the current directory.
#
# This program will do a animated transition to the new given image.
#
# If no "animate" is running, one will be started.  If no "last_image" file
# is found the last image is assumed to be black.
#
# Note that all images given should be all the same size!
#
####
#
last_image_file=last_image    # make this $HOME/.last_image  ???

next_image=`realpath "$1"`

# I use a temporary file so that I can background the "animate" command
temp=/tmp/slideshow.$$.miff
trap "rm -f $temp; exit 10" 1 2 3 15
trap "rm -f $temp; exit 0" 0

if [ -s "$last_image_file" ]; then
  convert "`cat last_image | tr -d '\012'`"  miff:-
else
  convert "$next_image" -gamma 0 miff:-
fi |
  # Do you complex image transition here
  # The final delay is minimum display time
  convert - "$next_image" -morph 10 \
          \( +clone -set delay 500 \) +swap +delete \
          $temp

# 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 3

# replace the transition image with a loop of the new image
animate -delay 100 -remote "$next_image" &

echo -n $next_image > last_image