An Acorn (macOS) script to add a drop shadow to screenshots of shadow-less windows

Add shadow to window screenshow.applescript

-- This script uses Acorn (tested with version 6.6.4)
-- to add a light border around a window screenshot.
--
-- Screenshots (without the huge macOS shadows) are made by shift-cmd-4, then space bar,
-- then option-click on window (see https://apple.stackexchange.com/a/120017/17533)
--
-- Before use, you need to create a Preset Filter for this, once:
--   With an image opened, use from menu: Filter / Stylize / Drop Shadow…
--   Set its options as you prefer (e.g. X/Y offset 0, Blur Radius 2, Opacity 80%),
--   then save it by clicking the gear icon, choose "Save Filter Preset…" and
--   name it: Frame Window Screenshot
--
-- To use, open the screenshot in Acorn, then run this script.
-- 
-- Written 16Apr21 by Thomas Tempelmann, http://apps.tempel.org

tell application "Acorn"
	
	set theDoc to front document
	
	-- increase img size by 2 pixel on each side
	set newWidth to (width of theDoc) + 4
	set newHeight to (height of theDoc) + 4
	resize canvas theDoc width newWidth height newHeight anchor position middle center
	
	-- add a (centered) shadow on all sides
	load filter preset theDoc name "Frame Window Screenshot"
	do filter theDoc name "Frame Window Screenshot"
	
end tell