#!/bin/sh
#
# polaroid_series images...  > result.jpg
#
# Generate a sequence of overlaping random angle polaroid images,
# from the given images.  The final JPEG image is output to stdout.
#
# This generates the polaroid thumbnails then uses a seperate command to layer
# them in a left to right sequence.
#
####
# Program Notes...
#
#  The new -layers merge  is used so that I don't have to worry about kepping
#  all the offsets positive.
#

tmpfile=/tmp/polariod_series.$$.png
trap "rm -f $tmpfile; exit 0" 0
trap "exit 2" 1 2 3 15


center=0     # Current center location for the next image.
             # This can be any number as I correctly handle the formating
             # of images which may generate given a negative offset.

offset=100   # Distance to the next images center. This can be negative!

background=LightSteelBlue   # background canvas color

for image in "$@"; do

   # read, thumbnail, polaroid image to a temp file.
   # I used super-sampled polariod to make the result better
   # This could have been done in a previous step to this loop
   convert -size 500x500 "$image" -thumbnail 240x240 \
       -set caption '%t' -bordercolor Lavender -background black \
       -pointsize 12  -density 96x96  +polaroid  -resize 50% \
       "$tmpfile"

   # Now gather image size, half it, and determine its virtual canvas
   # location so as to place it's center at the current position.
   xpos=`convert "$tmpfile" -format "%[fx: $center - w/2 ]" info:`
   ypos=`convert "$tmpfile" -format "%[fx: - h/2 ]" info:`

   # $xpos may be positive, in which case it needs to have a '+' sign
   # $ypos is always negative (but check its formating anyway)
   xpos=`echo "+$xpos" | sed 's/+-/-/'`
   ypos=`echo "+$ypos" | sed 's/+-/-/'`
   pos="$xpos$ypos"

   # Output the image into the pipeline for placement on canvas positioning
   # the images top-left corner on that canvas.
   #
   # It would be nice if gravity/justification could be used to position
   # centers, then we would not need to read the image size ourselves!
   #
   convert -page $pos "$tmpfile" MIFF:-

   # Increment position for next image  (lets use IM for the math ;-)
   center=`convert xc: -format "%[fx: $center + $offset ]" info:`

done |

  # Now we read the pipeline of the images output from the above loop
  # and create the canvas.  Repage the virtual canvas, add some extra
  # border space and output it.
  convert -background "$background"  MIFF:- \
          -layers merge +repage \
          -bordercolor "$background" -border 5x5  JPEG:-