#!/bin/sh
#
# pic2graph -- compile PIC image 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 a pic/eqn diagram on stdin, emit cropped bitmap on stdout.
# The pic markup should *not* be wrapped in .PS/.PE, this script will do that.
# An -unsafe 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).  An -eqn option changes the eqn delimiters.
# All other options are passed to convert(1).  The default format in PNG.
#
# 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. Only the -U option of gpic(1) is relevant.  -C doesn't matter because
#    we're generating our own .PS/.PE, -[ntcz] are irrelevant because we're
#    generating Postscript.
#
# 2. Ditto for groff(1), though it's a longer and more tedious demonstration.
#
# 3. Many options of convert(1) are potentially relevant (especially 
#    -density, -interlace, -transparency, -border, and -comment).
#
# Thus, we pass -U to gpic and groff, and everything else to convert(1).
#
# We don't have complete option coverage on eqn because this is primarily
# intended as a pic translator; we can live with eqn defaults. 
#
# $Id: pic2graph.sh,v 1.2 2002/07/17 04:55:46 wlemb Exp $
#
groffpic_opts=""
gs_opts=""
convert_opts=""
format="png"
eqndelim='$$'

while [ "$1" ]
do
    case $1 in
    -unsafe)
	groffpic_opts="-U";;
    -format)
	format=$2
	shift;;
    -eqn)
	eqndelim=$2
	shift;;
    -v | --version)
	echo "GNU pic2graph (groff) version 1.18.1"
	exit 0;;
    --help)
	echo "usage: pic2graph [ option ...] < in > out"
	exit 0;;
    *)
	convert_opts="$convert_opts $1";;
    esac
    shift
done

if [ "$eqndelim" ]
then
    eqndelim="delim $eqndelim"
fi

# Here goes:
# 1. Wrap the input in dummy .PS/PE macros (and add possibly null .EQ/.EN)
# 2. Process through eqn and pic to emit troff markup.
# 3. Process through groff to emit Postscript.
# 4. Use convert(1) to crop the PostScript and turn it into a bitmap.
tmp=/tmp/pic2graph-$$
trap "rm ${tmp}.*" 0 2 15 
(echo ".EQ"; echo $eqndelim; echo ".EN"; echo ".PS"; cat; echo ".PE") | \
       groff -e -p $groffpic_opts -Tps >${tmp}.ps \
       && convert -crop 0x0 $convert_opts ${tmp}.ps ${tmp}.${format} \
       && cat ${tmp}.${format}

# End
