AppleScriptでiTunesのジャケット取得

以下でとれるそうです。なんでもジャケット情報の先頭223byteを取り除くとファイルがとれるそうです。223byteに何が入っているのかは不明・・・

tell application "iTunes"
set theTrack to item 1 of selection
set theData to data of artwork 1 of theTrack
set theFormat to format of artwork 1 of theTrack as string
if theFormat contains "JPEG" then
set extension to ".jpg"
else if theFormat contains "PNG" then
set extension to ".png"
else
beep
return
end if
set theFile to ((path to desktop) & "artwork.bin" as string)
set des to open for access theFile with write permission
write theData to des
close access des
set theNewFile to ((path to desktop) & "artwork.png" as string)
set cmd to "tail -c +223 " & POSIX path of theFile & " > " & POSIX path of theNewFile
do shell script cmd