tell application "OmniGraffle"
	set thisWindow to first window
	set thisDocument to front document
	set thisCount to 0
	set win_layers to (thisWindow's canvas's layers)
	set canvasName to (thisWindow's canvas's name)
	set area type of current export settings to current canvas
	
	-- First we have to make every layer except for the 
	-- base layer invisible:
	repeat with win_layer from (count win_layers) to 1 by -1
		set thisLayer to item win_layer of win_layers
		if win_layer = (count win_layers) then
		else
			set visible of thisLayer to false
		end if
	end repeat
	
	-- Now, let's switch them on - one after another - and
	-- create a PNG out of the result:
	repeat with win_layer from (count win_layers) to 1 by -1
		set thisLayer to item win_layer of win_layers
		set visible of thisLayer to true
		set thisCount to thisCount + 1
		set targetFile to (thisDocument's path & "-" & canvasName & "-" & thisCount & ".png")
		save thisDocument as "PNG" in POSIX file targetFile
	end repeat
end tell