#!/bin/sh
#
# segment_image  input_image  multi_output_image
#
# Image of solid color areas (segments) seperate the image into a sequence
# of images, with each image containing one unconnected color segment on a
# transparent background.
#
# For more details see ImageMagcik Forum Discussion...
#   http://www.imagemagick.org/discourse-server/viewtopic.php?f=1&t=11705
#
# Future option: limit extraction to a specific color, generally white or
# black Or anything that is 'NOT' the background color (0,0 pixel color?).
#
# The 'fuzz factor' for floodfill removals may not work well, as the starting
# point is on the edge of a segment.  A better way to select segments may be
# to use a 'distance' morphological function, and then remove segments based
# on a larger distance value so as to avoid the segment edges.
#
# Anthony Thyssen    18 July 2008
#
PROGNAME=`type $0 | awk '{print $3}'`  # search for executable on path
PROGDIR=`dirname $PROGNAME`            # extract directory of program
PROGNAME=`basename $PROGNAME`          # base name of program

tmpdir=/tmp/$PROGNAME.$$
mkdir $tmpdir
if [ $? -ne 0 ]; then
  echo >&2 "$PROGNAME: Failed to create directory \"$tmpdir\" -- ABORTING"
  exit 1
fi
trap "rm -rf $tmpdir; exit 0" 0
trap "rm -rf $tmpdir; exit 1" 1 2 3 15


fuzz='0%'    # fuzz factor for flood filling sepearte colored areas
             # This may be needed for JPEG image input.

# ----------------------

# Read input image, once only as it may part of a pipeline of commands,
# and save a MPC working image, for fast image reading.
# Actually it may be better to just save as a IM TXT image file instead.
convert "$1" -matte $tmpdir/working.mpc

while true; do

  # Find the first non-transparent pixel in inpit image.
  coords=`convert $tmpdir/working.mpc txt:- | sed '1d; / 0)/d; s/:.*//; q'`

  # If image is now only transparent, all segments found
  [ -z "$coords" ]  && break

  echo >&2 "Extracting segment at coord $coords..."
  # Write the image to the output pipeline BEFORE the segment is removes
  # Only THEN, remove that segment from working image (mask),
  # Write the working image back so we can look for another segment.
  convert $tmpdir/working.mpc   -write miff:-   \
          -fuzz $fuzz -fill none -draw "matte $coords floodfill" \
          $tmpdir/working.mpc

done |
  # Reverse image list so 'segments' are 'added' on each consecutive image,
  # then use 'OptimizeTransparency' to make previously added pixels
  # transparent, leaving just the newly added pixels. Reverse the list back to
  # the order of discovery and output as a multi-image image sequence.
  convert miff:- -reverse -layers OptimizeTransparency -reverse "$2"