option "fg" - "Foreground (FG) or 'inside' value" double no default="1"
option "bg" - "Background (BG) or 'ouside' value" double no default="0"
-option "useFG" - "Use FG value (if not keep values from input)" flag off
-option "useBG" - "Use BG value (if not keep values from input)" flag off
+option "mode" - "Use FG and/or BG values (if FG, the BG is replaced by the input image values)" values="FG","BG","both" default="both" no
+