This is a quick AppleScript written to shrink wide images to at most 1200px. To use it, open it in Script Editor, then save it as an Application, and drag files on to its icon in Finder. Target width is set in line 17. We can similarly use it to shrink tall images if we want to.

image-width-rescaler

on open some_images
  repeat with my_image in some_images
		try
			rescale_and_copy(my_image)
		end try
	end repeat
end open

to rescale_and_copy(my_item)
	tell application "Image Events"
		launch
		
		-- Change the width as appropriate here
		set the target_width to 1200
		
		-- Open the image
		set my_image to my_item
		
		set my_type to my_image's file type
		
		copy dimensions of this_image to {current_width, current_height}
		
		-- Scale the image as appropriate
		if current_width is greater than target_width then
			scale my_image to size target_width
		end if
		
		-- Make a new copy with the prefix "scaled"		
		tell application "Finder" to set new_item to ¬
			(container of my item as string) & "scaled." & (name of my_item)
		save my_image in new_item as my_type
		
	end tell
end rescale_and_copy