#!/bin/sh
# interlace-gif.sh --- make a gif be interlaced, or not.
# Copyright © 1996, 2000 Jamie Zawinski <jwz@jwz.org>
#
# Permission to use, copy, modify, distribute, and sell this software and its
# documentation for any purpose is hereby granted without fee, provided that
# the above copyright notice appear in all copies and that both that
# copyright notice and this permission notice appear in supporting
# documentation.  No representations are made about the suitability of this
# software for any purpose.  It is provided "as is" without express or 
# implied warranty.
#
# Requires the following programs:
#
#	giftrans (1.11.1)
#	giftoppm or giftopnm (any version)
#	ppmtogif (netpbm 1)

# If you have giftopnm but not giftoppm, change this line:
giftoppm=giftopnm
#giftoppm=giftoppm

usage()
{
  echo "usage: $0 [-interlace|-deinterlace] GIFs ..."
  exit 1
}

set -e
#set -x

interlacep=True

case $1 in
 -deinterlace )
    interlacep=False
    shift
    ;;
 -interlace )
    interlacep=True
    shift
    ;;
 -* )
    usage
    ;;
esac

TMP=/tmp/IG$$
TMP2=/tmp/IG$$2


find_transparent_color()
{
  file="$1"
  giftrans -L $file > $TMP 2>&1
  index=`sed -n "s@.*Transparent Color Index: \(.*\)@\1@p" < $TMP`
  color=`sed -n "s@.*Color ${index}: .*#\([0-9a-fA-F][0-9a-fA-F]*\).*@\1@p" \
		< $TMP`
  rm -f $TMP
  if [ "$color" = "" ]; then
    echo "$0: couldn't determine transparent color of $file" >&2
  else
    echo $color
  fi
}


for file in $* ; do
  intp=`giftrans -L $file 2>&1 | sed -n 's@.*Interlace Flag: \(.*\)@\1@p'`
  if [ "$interlacep" = True -a x"$intp" = xTrue ]; then
    echo "$file: gif is already interlaced." >&2
  elif [ "$interlacep" = False -a x"$intp" = xFalse ]; then
    echo "$file: gif is already non-interlaced." >&2
  else
    transp=`giftrans -L $file 2>&1 |
		sed -n 's@.*Transparent Color Flag: \(.*\)@\1@p'`
    color=""
    trans_args=""

    if [ x"$transp" = xTrue ]; then
      if ( ppmtogif -help 2>&1 | grep transparent >&- ) then
	color=`find_transparent_color $file`
	trans_args="-transparent #$color"
      else
	echo "$0: ppmtogif does not support the -transparent flag."
	exit 1
      fi
    fi

    if [ x"$transp" = xTrue -a "$color" = "" ]; then
      echo -n #noop
    else
      if [ "$interlacep" = True ]; then
	if ( ppmtogif -help 2>&1 | grep interlace >&- ) then
	  echo "$0: converting $file to an interlaced gif..." >&2
	else
	  echo "$0: ppmtogif does not support the -interlace flag."
	  exit 1
	fi
      else
        echo "$0: converting $file to a non-interlaced gif..." >&2
      fi
      rm -f $TMP
      cp $file $TMP
      if [ "$interlacep" = True ]; then
        $giftoppm < $TMP | ( ppmtogif $trans_args -interlace > $TMP2 2>&- )
      else
        $giftoppm < $TMP | ( ppmtogif $trans_args > $TMP2 2>&- )
      fi
 ls -lFi $TMP $TMP2
      rm -f $TMP
      cp -p $TMP2 $file
 ls -lFi $TMP2 $file
      rm -f $TMP2
      ls -lF $file
    fi
  fi

done