#!/bin/sh
#
# pic2png -- compile PIC image descriptions to PNG bitmaps
#
# by Eric S. Raymond <address@hidden>, July 2001
#
# In Unixland, the magic is in knowing what to string together...
#
# Take a pic diagram on standard input, emit cropped PNG on standard output.
# The pic markup should *not* be wrapped in .PS/.PE, this script will do that.
# Does PNG because it's as good as any other bitmap format and freer than most.
# A -U option on the command line enables gpic/groff "unsafe" mode.
# All other options are passed to pnmtopng.
#
# Requires groff, ghostscript, and the pnm tools.  All are open source.
# Use, modify, and redistribute freely.  Send me fixes and enhancements.
#
# 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. No options of pnmcrop are relevant.  We can assume the generated image
# is going to be black-on-white because that's what pic generates.  Even
# if pic were somehow coerced into generating a non-white background,
# pnmcrop's algorithm (look at the top corners) will find the right
# thing because gs(1) is generating a full page.
#
# 4. Many options of pnmtopng(1) are potentially relevant (especially
# -interlace, -transparent, -background, -text, and -compression.
#
# Thus, we pass -U to gpic and groff, and everything else to pnmtopng.
#
# $Id: pic2png,v 1.1 2001/07/18 03:07:41 esr Exp $
#
groffpic_opts=""
pnmtopng_opts=""

while [ "$1" ]
do
    case $1 in
	-unsafe) groffpic_opts="-U"; pngtopnm_opts="$pngtopnm_opts -U";;
        *)  pnmtopmg_opts="$pnmtopmg_opts $1" ;;
    esac
    shift;
done

# Here goes:
# 1. Wrap the input in dummy .PS/PE macros
# 2. Process through pic to emit troff markup
# 3. Process through groff to emit Postscript
# 4. Process through ghostscript to emit a ppm bitmap
# 5. Crop the ppm bitmap
# 6. Turn the ppm into PNG
(echo ".PS"; cat; echo ".PE") \
	| pic $groffpic_opts \
	| groff $groffpic_opts -Tps \
 	| gs -q -sDEVICE='ppmraw' -sOutputFile='-' -dNOPAUSE -dBATCH - \
	| pnmcrop \
	| pnmtopng $pnmtopmg_opts

# End