http://woodgears.ca/eyeball/

This score was not my first try.

Your inaccuracy by category:

Parallelogram ---- 5.7 - 2.2 - 1.0
Midpoint -------- 1.0 - 2.2 - 3.2
Bisect angle ---- 9.2 - 2.0 - 8.5
Triangle center - 5.0 - 2.1 - 5.6
Circle center --- 1.4 - 1.4 - 2.8
Right angle ----- 1.5 - 1.6 - 0.3
Convergence --- 4.2 - 5.1 - 1.4

Average error: 2.78 (lower is better)