unpack Autodesk Sketchbook multi-layered TIFF to PNGs

sketchbook_unpack.sh

#!/usr/bin/env bash
# sketchbook_unpack.sh
# unpack Autodesk Sketchbook multi-layered TIFF to PNGs
#
# requires: libtiff, imagemagick
# reference: https://www.awaresystems.be/imaging/tiff/tifftags/docs/alias.html

input="$1"

test -f "$input" || (echo "usage: $0 TIFF_FILE" && exit 1)

dir=`dirname "$input"`
base=`basename "$input" .tiff`
outdir="$input.dir"

mkdir "$outdir"

tiffinfo "$input" >"$input.info" 2>/dev/null
cwidth=`grep 'Image Width' "$input.info" | sed 's/.*Width: \([0-9]*\).*/\1/'`
cheight=`grep 'Image Length' "$input.info" | sed 's/.*Length: \([0-9]*\).*/\1/'`

grep SubIFD "$input.info" | sed -e 's/^.*: //' -e 's/ /\n/g' |\
while read line; do
	output="$dir"/"$base"_"$line".tiff
	info="$dir"/"$base"_"$line".tmp
	tiffinfo -o $line "$input" > "$info" 2>/dev/null

	if ! grep -q 'reduced-resolution image (1 = 0x1)' "$info" ; then

		pos_x=`grep Position "$info" | sed 's/.*: \([0-9]*\).*/\1/'`
		pos_y=`grep Position "$info" | sed 's/.*, \([0-9]*\)$/\1/'`
		width=`grep 'Image Width' "$info" | sed 's/.*Width: \([0-9]*\).*/\1/'`
		height=`grep 'Image Length' "$info" | sed 's/.*Length: \([0-9]*\).*/\1/'`

		off_x=`expr 0$pos_x`
		off_y=`expr 0$cheight - 0$pos_y - 0$height`

		tiffcp -o $line "$input" "$output" 2>/dev/null

		magick "$output" \
			-flip \
			-separate -swap 0,2 -combine \
			-set page "$cwidth"x"$cheight"+"$off_x"+"$off_y" \
			-background none \
			-flatten \
			"$outdir/$base"_"$line.png"

		rm "$output"

	fi
	rm "$info"
done

rm "$input.info"

TODO: find a way to compose layers into a PSD, imagemagick produces corrupted psd with current outputed PNGs.