Automator shrink images larger than X

Automator is great at running linear workflows. It really falls down when you have any logic or flow needs (e.g. if/then statements, loops, etc.)

In this case you're likely to need to step out to a shell or AppleScript where you have a lot more control over logic flows.

For example, here's an AppleScript you can incorporate into your workflow via a Run AppleScript action. It takes a file and determine the pixel height and width. If either exceeds 4000, it resizes the image using the built-in sips command (there are other ways of doing this, too:

on run {input, parameters}
	
	repeat with theImage in input
		set theFilePath to quoted form of POSIX path of theImage
		
		set theWidth to last word of (do shell script "sips -g pixelWidth " & theFilePath) as integer
		set theHeight to last word of (do shell script "sips -g pixelHeight " & theFilePath) as integer
		
		if theWidth > 4000 or theHeight > 4000 then
			do shell script "sips -Z 1200 " & theFilePath
		end if
	end repeat
	return input
end run