#! /bin/sh

# convert an 18x18 BDF font into a corresponding 20x20 BDF font
# padding an empty margin of 1 pixel to each side

padfont () {
	echo Calculating shifted font cells for font "$1" >&2
	echo This may take 30 minutes or more, please be patient >&2

	(
	LC_ALL=C sed -f - $1 <<\/EOS
# convert an 18x18 BDF font into a corresponding 20x20 BDF font
# padding an empty margin of 1 pixel to each side


# prefix pixel pattern with a function call that calculates the shift
s,^\([0-9A-F][0-9A-F][0-9A-F][0-9A-F][0-9A-F][0-9A-F]\)$,pix \1,
t

# pad upper and lower margin with 1 line of blank pixels each
/^BITMAP/ a\
echo 000000

/^ENDCHAR/ i\
echo 000000


# adapt font name and properties
s,^\(FONT .*\)-18-120-100-100-\([^-]*\)-180-,\1-20-200-75-75-\2-200-,
s,^SIZE 12 100 100,SIZE 20 75 75,
s,^FONTBOUNDINGBOX 18 18 ,FONTBOUNDINGBOX 20 20 ,
s,^FONT_ASCENT 15,FONT_ASCENT 16,
s,^FONT_DESCENT 3,FONT_DESCENT 4,
s,^PIXEL_SIZE 18,PIXEL_SIZE 20,
s,^POINT_SIZE 120,POINT_SIZE 200,
s,^RESOLUTION_X 100,RESOLUTION_X 75,
s,^RESOLUTION_Y 100,RESOLUTION_Y 75,
s,^AVERAGE_WIDTH 180,AVERAGE_WIDTH 200,

# adapt character properties
s,^SWIDTH 1080 ,SWIDTH 960 ,
s,^DWIDTH 18 ,DWIDTH 20 ,
s,^BBX 18 18 ,BBX 20 20 ,


# escape single quote marks, quote lines and add echo command
s,','\\'',g
s,^,echo ',
s,$,',


# prepend shell command for pixel shift calculation
1 i\
pix () {\
	n=`printf %d 0x$*`\
	printf '%06X\\n' `expr $n / 2`\
}\


# end
/EOS
) | sh
}

case "$1" in
"")	echo Transforming all 18x18 fonts in current directory to 20x20 >&2 ;;
esac

for f in ${*-18x18*.bdf}
do	f20=`echo $f | sed -e "s,18,20,g"`
	if [ -f $f20 ]
	then	echo Font file $f20 already exists. Rename / Remove, then repeat >&2
	else	echo Transforming $f to $f20 >&2
		padfont $f > $f20
	fi
done