Maybe this is what you want:
gr = Graphics[(* your graphics *)];
AbsoluteOptions[gr]
EDIT:
Probably better is to avoid directives like Large at all, e.g.:
Graphics[{AbsoluteThickness[3], Green, Rectangle[{0, -1}, {2, 1}],
Red, Disk[], Blue, Circle[{2, 0}], Yellow,
Polygon[{{2, 0}, {4, 1}, {4, -1}}], Purple, Arrowheads[.1],
Arrow[{{4, 3/2}, {0, 3/2}, {0, 0}}], Black,
AbsoluteDashing[{10, 20}], Line[{{-1, 0}, {4, 0}}]}]
Does that help?
