#!/bin/sh

case $# in
3)
	;;
*)
	echo "Usage: $0 <input.svg> <size> <output.png>" 1>&2
	exit 1
	;;
esac

SVG=$1
SIZE=$2
PNG=$3

SHADOW=$(($SIZE / 16))

OPACITY=60
BLUR=$(($SHADOW / 2))

if [ $BLUR = 0 ]; then
    BLUR=1
fi

SHIFT=$(($SHADOW * 3 / 4))

IMAGE=$(($SIZE - $SHIFT - $BLUR))

TMP=image-$$.png

trap "rm $TMP" 0 1 15

rsvg-convert -w $IMAGE -h $IMAGE -o $TMP $SVG

convert $TMP \
	\( +clone -background black -shadow ${OPACITY}x${BLUR}+${SHIFT}+${SHIFT} \) \
	+swap -background none -layers merge -crop ${SIZE}x${SIZE}+0+0 +repage $PNG