#!/bin/bash
#
# Script to produce rasterised LaTeX formulae
# Dependencies: pdflatex, ghostscript, imagemagick
# Brad Atcheson
# 7 Nov 2008

USAGE="Usage: `basename "$0"` '<latex>' output.png
Produces rasterised LaTeX formulae
Remember to enclose the latex commands in single quotes (eg 'x^0')
The displaymath environment is assumed
Options:
	[-r resolution in DPI (default:300)]
	[-h help]"

# print usage info to stderr
if [ "$#" == "0" ]; then
	echo "$USAGE" 1>&2
	exit 1
fi

# parse cmdline
dpi=300
while getopts ":r:h" options
do
	case $options in
		r ) dpi=$OPTARG;;
		h ) echo "$USAGE" 1>&2; exit 1;;
		* ) echo "Unrecognised argument: $options" 1>&2; exit 1;;
	esac
done
shift $(($OPTIND - 1))

# build the temp tex file
# keep it as small as possible to avoid wasting time/mem rasterising
# the blank space on the page. Hopefully 6"x3" will be large enough for
# most inputs. If not, just make the page a little bigger here
file="temp.$RANDOM"
pagewidth="6in"
pageheight="3in"
echo "\documentclass{article}" >$file.tex
echo "\pagestyle{empty}" >>$file.tex
echo "\pdfpagewidth=$pagewidth" >>$file.tex
echo "\pdfpageheight=$pageheight" >>$file.tex
echo "\setlength{\voffset}{-1in}" >>$file.tex
echo "\setlength{\topmargin}{0pt}" >>$file.tex
echo "\setlength{\headheight}{0pt}" >>$file.tex
echo "\setlength{\headsep}{0pt}" >>$file.tex
echo "\setlength{\hoffset}{-1in}" >>$file.tex
echo "\setlength{\marginparwidth}{0pt}" >>$file.tex
echo "\setlength{\oddsidemargin}{0pt}" >>$file.tex
echo "\setlength{\marginparsep}{0pt}" >>$file.tex
echo "\setlength{\footskip}{0pt}" >>$file.tex
echo "\setlength{\textwidth}{$pagewidth}" >>$file.tex
echo "\setlength{\textheight}{$pageheight}" >>$file.tex
echo "\begin{document}" >>$file.tex
echo "\begin{displaymath}" >>$file.tex
echo "$1" >>$file.tex
echo "\end{displaymath}" >>$file.tex
echo "\end{document}" >>$file.tex

# produce a fullpage pdf
pdflatex -halt-on-error $file.tex >/dev/null
if [ ! -f $file.pdf ];
then
	echo "Error running pdflatex. See $file.log for details" 1>&2
	rm $file.aux
	exit 2
fi
rm $file.{aux,log}

# get the bounding box
box=`gs -q -dBATCH -dNOPAUSE -sDEVICE=bbox $file.pdf 2>&1 | grep Hi`
blx=`echo $box | cut -d " " -f 2`
bly=`echo $box | cut -d " " -f 3`
trx=`echo $box | cut -d " " -f 4`
try=`echo $box | cut -d " " -f 5`
width=`echo "$trx-$blx" | bc -l`
height=`echo "$try-$bly" | bc -l`

# scale and round coordinates (depends on resolution)
# and add a one-pixel border
width=`printf "%.0f" $(echo "$width / 72 * $dpi + 2" | bc -l)`
height=`printf "%.0f" $(echo "$height / 72 * $dpi + 2" | bc -l)`
originx=`printf "%.0f" $(echo "$blx / 72 * $dpi - 1" | bc -l)`
originy=`printf "%.0f" $(echo "$bly / 72 * $dpi - 1" | bc -l)`

# convert cropped region to bitmap, flipping coordinate system
# because pdf uses bottom-left as origin
convert -density $dpi $file.pdf \
		-gravity SouthWest \
		-crop ${width}x${height}+${originx}+${originy} \
		+repage \
		"$2"

# cleanup
rm $file.{pdf,tex}