-option "fg" - "Foreground (FG) or 'inside' value" double optional default="1"
-option "bg" - "Background (BG) or 'ouside' value" double optional default="0"
-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" optional