Aquí hay un simple Applescript que usa los Eventos de Imagen integrados en OS X. Agregue sal al gusto.
property kFileList : {}
tell application "Finder"
set theSourceFolder to choose folder
set theDestinationFolder to choose folder
my createList(theSourceFolder)
set lastItem to (count kFileList)
repeat with thisItem from 1 to lastItem
set theFile to (theSourceFolder & item thisItem of kFileList) as string
tell application "Image Events"
set theImage to open theFile
save theImage as JPEG2 in ((theDestinationFolder & item thisItem of kFileList & ".jpg") as string) with compression level high
end tell
end repeat
end tell
on createList(mSource_folder)
set item_list to ""
tell application "System Events"
set item_list to get the name of every disk item of mSource_folder
end tell
set item_count to (get count of items in item_list)
repeat with i from 1 to item_count
set the_properties to ""
set the_item to item i of the item_list
set the_item to ((mSource_folder & the_item) as string) as alias
tell application "System Events"
set file_info to get info for the_item
end tell
if visible of file_info is true then
set file_name to displayed name of file_info
set end of kFileList to file_name
if folder of file_info is true then
my createList(the_item)
end if
end if
end repeat
end createList
Acorn también es bueno para la automatización barata y fácil a través de Applescript que ofrecerá más opciones que Image Events, pero Image Events es gratis así que ahí está