#! /bin/sh
#
# eqn2graph -- compile EQN equation descriptions to bitmap images
#
# by Eric S. Raymond <esr@thyrsus.com>, July 2002
#
# In Unixland, the magic is in knowing what to string together...
#
# Take an eqn equation on stdin, emit cropped bitmap on stdout.
# The pic markup should *not* be wrapped in .EQ/.EN, this script will do that.
# A -U option on the command line enables gpic/groff "unsafe" mode.
# A -format FOO option changes the image output format to any format
# supported by convert(1).  All other options are passed to convert(1).
# The default format is PNG.
#
# This is separate from pic2graph because pic processing has some weird
# clipping effect on the output, mangling equations that are very wide 
# or deep.  Besides, this tool can supply its own delimiters.
#

# Requires the groff suite and the ImageMagick tools.  Both are open source.
# This code is released to the public domain.
#
# Here are the assumptions behind the option processing:
#
# 1. None of the options of eqn(1) are relevant.
#
# 2. Only the -U option of groff(1) is relevant.
#
# 3. Many options of convert(1) are potentially relevant, (especially 
# -density, -interlace, -transparency, -border, and -comment).
#
# Thus, we pass -U to groff(1), and everything else to convert(1).
#
groff_opts=""
convert_opts=""
format="png"

while [ "$1" ]
do
    case $1 in
    -unsafe)
	groff_opts="-U";;
    -format)
	format=$2
	shift;;
    -v | --version)
	echo "GNU eqn2graph (groff) version @VERSION@"
	exit 0;;
    --help)
	echo "usage: eqn2graph [ option ...] < in > out"
	exit 0;;
    *)
	convert_opts="$convert_opts $1";;
    esac
    shift
done

# create temporary directory
tmp=
for d in "$GROFF_TMPDIR" "$TMPDIR" "$TMP" "$TEMP" /tmp; do
    test -z "$d" && continue

    tmp=`(umask 077 && mktemp -d -q "$d/eqn2graph-XXXXXX") 2> /dev/null` \
    && test -n "$tmp" && test -d "$tmp" \
    && break

    tmp=$d/eqn2graph$$-$RANDOM
    (umask 077 && mkdir $tmp) 2> /dev/null && break
done;
if test -z "$tmp"; then
    echo "$0: cannot create temporary directory" >&2
    { (exit 1); exit 1; }
fi

trap 'exit_status=$?; rm -rf $tmp && exit $exit_status' EXIT INT TERM

# Here goes:
# 1. Add .EQ/.EN.
# 2. Process through eqn(1) to emit troff markup.
# 3. Process through groff(1) to emit Postscript.
# 4. Use convert(1) to crop the Postscript and turn it into a bitmap.
read equation
(echo ".EQ"; echo 'delim $$'; echo ".EN"; echo '$'"$equation"'$') | \
	groff -e $groff_opts -Tps -P-pletter > $tmp/eqn2graph.ps \
	&& convert -trim $convert_opts $tmp/eqn2graph.ps $tmp/eqn2graph.$format \
	&& cat $tmp/eqn2graph.$format

# End
