#!/bin/sh
#
# eqn2graph -- compile EQN equation descriptions to bitmap images
#
# by Eric S. Raymond <[email protected]>, 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).
#
# $Id: eqn2graph.sh,v 1.2 2002/07/17 04:55:46 wlemb Exp $
#
groff_opts=""
convert_opts=""
format="png"

while [ "$1" ]
do
case $1 in
-unsafe)
groff_opts="-U";;
-format)
format=$2
shift;;
-v | --version)
echo "GNU eqn2graph (groff) version 1.18.1.4"
exit 0;;
--help)
echo "usage: eqn2graph [ option ...] < in > out"
exit 0;;
*)
convert_opts="$convert_opts $1";;
esac
shift
done

# 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.

tmpps=`mktemp /tmp/eqn2graph-XXXXXXXX.ps`
tmpfmt=`mktemp /tmp/eqn2graph-XXXXXXXX.$format`
trap "rm $tmpps $tmpfmt" 0 2 15
read equation
(echo ".EQ"; echo 'delim $$'; echo ".EN"; echo '$'"${equation}"'$') | \
groff -e $groff_opts -Tps >$tmpps \
&& convert -crop 0x0 $convert_opts $tmpps $tmpfmt \
&& cat $tmpfmt

# End