property Main_folder : missing value
set Main_folder to choose folder

tell application "QuickTime Player"
if not (exists movie 1) then error "No movies are open."
stop movies
tell front movie to set {currMovie, T_name, duration_list, current time} to ¬
{it, text 1 thru -5 of (get name), duration of chapters of (get first track whose kind is "Sprite"), 0}
set T_target to my makeFolder(T_name)

repeat with i from 1 to (count duration_list)
tell currMovie
set current time to current time + (item i of duration_list)
export to (T_target & T_name & " Chapter " & i) as picture using settings preset "Photo-JPEG" -- or "Uncommpressed", or "PNG"
end tell
end repeat
end tell

on makeFolder(n)
tell application "Finder" to return (make new folder at Main_folder with properties {name:"Images from Movie " & n}) as Unicode text
end makeFolder