Help with selecting files from script menu or drag and drop

Question

I found this scale images applescript online. It works great when a bunch of files is dragged on top of the script but I would like it to also work when a folder or group of files is selected in the Finder and I activate it from the scripts menu.
I can't get my on run statement to work. I'm not really an Applescript guy so I'm really just asking if someone can help finish what I started in this on run.
-- save in Script Editor as Application
-- drag files to its icon in Finder
property target_width : 120
property save_folder : ""
on run
tell application "Finder"
activate
set folder_path to quoted form of (POSIX path of (the selection as alias))
set theItems to every file of folder_path
end tell
end run
on open some_items
-- do some set up
tell application "Finder"
-- get the target width, the default answer is the property target_width
set new_width to text returned of ¬
(display dialog "Target width:" default answer target_width ¬
buttons {"OK"} default button "OK")
if new_width as integer > 0 then
set target_width to new_width
end if
-- if the save_folder property has not been set,
-- set it to the folder containing the original image
if save_folder is "" then
set save_folder to ¬
(container of file (item 1 of some_items) as string)
end if
-- get the folder to save the scaled images in,
-- default folder is the property save_folder
set temp_folder to ¬
choose folder with prompt ¬
"Save scaled images in:" default location alias save_folder
set save_folder to temp_folder as string
end tell
-- loop through the images, scale them and save them
repeat with this_item in some_items
try
rescaleand_save(thisitem)
end try
end repeat
tell application "Image Events" to quit
end open
on rescaleand_save(thisitem)
tell application "Finder"
set new_item to save_folder & "scaled." & (name of this_item)
end tell
tell application "Image Events"
launch
-- open the image file
set this_image to open this_item
set typ to this_image's file type
copy dimensions of this_image to {current_width, current_height}
scale this_image by factor (target_width / current_width)
save this_image in new_item as typ
end tell
end rescaleandsave

Answer 1

When items are dragged to your script's icon they are passed in to the on open handler, so this triggers:
on open some_items
and the dragged items are passed in as some_items
In contrast, when you double-click on the script, or invoke it via the Script menu, this runs the on run handler:
on run
  tell application "Finder"
    activate
    folder_path to quoted form of (POSIX path of (the selection as alias))
    set theItems to every file of folder_path
  end tell
end run
However, there's nothing in this block that actually does anything with the selection - you (dangerously) assume that the selection is a folder (you really should check first), and just set theItems to every file in that folder then you exit.
So to do what you want you'll need to edit your run handler to filter the selection and pass files over to the code that does the hard work.
You already have the basis for this - your rescaleandsave() handler, so it's just a matter of identifying the files in the selection and passing those over to that handler:
on run
  tell application "Finder"
    set cur_selection to (get selection) -- get the selection
    repeat with each_item in cur_selection -- iterate through
      if class of each_item is folder then -- do we have a folder?
        set theFiles to every file of each_item -- if so, get its contents
        repeat with each_file in theFiles -- iterate through them
          my rescaleand_save(eachfile) -- and process them
        end repeat
      else if class of each_item is document file then -- do we have a file selected?
        my rescaleand_save(eachitem) -- if so, process it
      end if
    end repeat
  end tell
end run
So the idea here is that the run handler gets the selection and works through the (potentially-numerous) items. For each selected item it checks whether its a folder or a file, if its a folder it gets all the files within and passes them to the rescaleandsave handler.
Note that this is not recursive - it won't catch files within folders within folders - since it only looks at the top level of selected folders, but it wouldn't be hard to rework the script to handle that if that's what you need.