Script to transform Apple iTunes' .itc files into images (JPG or PNG)

itcToImageV2.1.sh

#!/bin/bash
# Script to transform Apple iTunes' .itc files into images (JPG or PNG)
#
# This is a mod of the very useful script by Matthieu Riegler (@kyro38) at 
#    https://github.com/kyro38/MiscStuff/blob/master/Useless/itc/itcToImageV2.sh
#
# The mods are 
#    * to use `find` rather than `gfind` (I'm on a Mac and find` works just fine 
#      and I don't need to install `coreutils` just for this task)
#    * to parameterize the source and destination directories for the .itc files
#    * to add some communication with the user
#    * to count the ITC files being processed in order to get a confirmation from the user
#
# My iTunes folder is usually nonstandard, I want to be able to run this on Album Artwork
# folders copied from others' machines (who don't want me hogging their machine for this
# effort), and I'm not consistent on my own machines whether I use the standard directory
# structure for iTunes.
#
# .itc files may be located in ~/Music/iTunes/Album Artwork unless you, like I,
#    have customized iTunes' directory
#
# This script uses (/!\ needs ) ImageMagick's convert, hexdump, printf and dd.
#
# "Newer" (>2012?) iTunes ITC files may contain ARGB content, with as many as 3 sizes 
#    of the same image in one ITC file. Because of that, and depending on the size 
#    of your artwork directory, this script might be a little slow. One alternative 
#    is Simon Kennedy's Python module: http://www.sffjunkie.co.uk/python-itc.html
#
# Have a nice day.

# Test for inputs, use defaults if absent
if [ -z $1 ]; then
	# absent any parameters, use defaults
	AlbumArtwork="${HOME}/Music/iTunes/Album Artwork"
	DestinationDir="$AlbumArtwork/Images"
	echo
	echo "Using default directories:"
	echo "    Source:     " $AlbumArtwork
	echo "    Destination:" $DestinationDir
else
	# Source dir
	AlbumArtwork=$1
	# Destination dir
	DestinationDir=$2
	echo
	echo "Using these directories:"
	echo "    Source:     " $AlbumArtwork
	echo "    Destination:" $DestinationDir
	echo
fi

# Get count of ITC files for notice to script executor
FileCount=`find "$AlbumArtwork" -name '*.itc' | wc -l`

read -r -p "About to extract all art from
    $AlbumArtwork
to
    $DestinationDir.

There are $FileCount .itc files to be processed.

Continue (y/n)? " choice
case "$choice" in 
  y|Y )
    echo "OK! Here we go."
    ;;
  n|N )
    echo "Abandoning script."
    exit 1
    ;;
  * )
    echo "Invalid response, exiting."
    exit 1
    ;;
esac

IFS=$'\n'

if [ ! -d "$DestinationDir" ]; then
	mkdir "$DestinationDir"
	echo "new Images dir"
fi

for file in `find "$AlbumArtwork" -name '*.itc'`; do
	start=0x11C
	exit=0;
	i=1;
	echo $file
	while [ 1 ]; do

		typeOffset=$(($start+0x30))
		imageType=$(hexdump -n 4 -s $typeOffset -e '"0x"4/1 "%02x" "\n"' $file)

		#If there is no next byte, jump to the next itc file.
		if [[ -z $imageType ]]; then
			break
		fi

		imageOffsetOffset=$(($start+8))

		itemSize=$(hexdump -n 4 -s $start -e '"0x"4/1 "%02x" "\n"' $file)
		imageOffset=$(hexdump -n 4 -s $imageOffsetOffset -e '"0x"4/1 "%02x" "\n"' $file)

		imageStart=$(($start+$imageOffset))
		imageSize=$(($itemSize-imageOffset))

		imageWidth=$(hexdump -n 4 -s $(($start+56)) -e '"0x"4/1 "%02x" "\n"' $file)
		imageWidth=$(printf "%d" $imageWidth)
		imageHeight=$(hexdump -n 4 -s $(($start+60)) -e '"0x"4/1 "%02x" "\n"' $file)
		imageHeight=$(printf "%d" $imageHeight)

		dir=$(dirname "$file")
		xbase=${file##*/} #file.etc
		xpref=${xbase%.*} #file prefix

		#echo $file
		#echo itemsize $itemSize
		#echo start $start
		#echo imageOffset $imageOffset
		#echo imageStart $imageStart
		#echo imageSize $imageSize
		#echo imageWidth $imageWidth
		#echo imageHeight $imageHeight

		if [[ $imageType -eq 0x504E4766 ]] || [[ $imageType -eq 0x0000000E ]] ; then
			targetFile="$DestinationDir/$xpref-$i.png"
			if [ ! -f "$targetFile" ]; then
				echo PNG
				dd skip=$imageStart count=$imageSize if="$file" of="$targetFile" bs=1 &> /dev/null
			fi
		elif [[ $imageType -eq 0x41524762 ]] ; then
			targetFile="$DestinationDir/$xpref-$i.png"
			if [ ! -f "$targetFile" ]; then
				echo ARGB
				dd skip=$imageStart count=$imageSize if="$file" of="$TMPDIR/test$i" bs=1 &> /dev/null

				#Using a matrix to convert ARGB to RGBA since imagemagick does only support rgba input
				convert -size $imageWidth"x"$imageHeight -depth 8 -color-matrix '0 1 0 0 0 0 1 0 0 0 0 1 1 0 0 0' rgba:"$TMPDIR/test$i" "$targetFile"
			fi
		elif [[ $imageType -eq 0x0000000D ]] ; then
			targetFile="$DestinationDir/$xpref-$i.jpg"
			if [ ! -f "$targetFile" ]; then
				echo JPG
				dd skip=$imageStart count=$imageSize if="$file" of="$targetFile" bs=1 &> /dev/null
			fi
		else
			echo $imageType
			exit=1
			break;
		fi

		start=$(($start+$itemSize))
		i=$(($i+1))
	done
done

Got it -- thank you for that!