Table 1.

Facial symmetry features, introduced by Parra-Dominguez et al. [6].

No.	Facial Region	Type	Formula
f0	Eyebrows	Angle	$\left|\angle (P0,P9)\right|$
f1	Eyebrows	Angle	$\left|\angle (P2,P7)\right|$
f2	Eyebrows	Angle	$\left|\angle (P4,P5)\right|$
f3	Eyebrows	Max.	$max(L/M,M/L)$
f4	Eyebrows	Slope	$m(P0,P9)$
f5	Eyebrows	Slope	$m(P2,P7)$
f6	Eyebrows	Slope	$m(P4,P5)$
f7	Eyes	Angle	$\left|\angle (P10,P19)\right|$
f8	Eyes	Max.	$max(B_l/B_r,B_r/B_l)$
f9	Eyes	Max.	$max(D/E,E/D)$
f10	Eyes	Max.	$max(H/I,I/H)$
f11	Eyes	Max.	$max(N/O,O/N)$
f12	Eyes	Max.	$max(N_l/O_r,O_r/N_l)$
f13	Eyes	Max.	$max(N_r/O_l,O_l/N_r)$
f14	Mouth	Angle	$\left|\angle (P28,P34)\right|$
f15	Mouth	Max.	$max(F/G,G/F)$
f16	Mouth	Max.	$max(P_l/Q_l,Q_l/P_l)$
f17	Mouth	Max.	$max(P_u/Q_u,Q_u/P_u)$
f18	Mouth	Max.	$max(V_l/A,V_r/A)$
f19	Mouth	Max.	$max(P_l/W,Q_l/W)$
f20	Mouth	Max.	$max(P_u/W,Q_u/W)$
f21	Mouth	Max.	$max(W_l/W,W_r/W)$
f22	Nose	Angle	$\left|\angle (P23,P27)\right|$
f23	Combined	Angle	$\left|\angle (P22,P37)\right|$
f24	Combined	Max.	$max(J/K,K/J)$
f25	Combined	Max.	$max(T/A,U/A)$
f26	Combined	Max.	$max(R/A,S/A)$
f27	Combined	Ratio	$C/A$
f28	Combined	Ratio	$X/A$

In f3, L and M are the average height of all the left and right eyebrow points, respectively. In f11, N = (N_l + N_r)/2, similarly, O = (O_l + O_r)/2. In f19, f20, and f21, W is the distance shown in Figure 2d, and the perimeter values W_l and W_r are computed as W_l = $\overline{\mathrm{S}}$(P28, P29, P30, P31, P37, P38, P39) and W_r = $\overline{\mathrm{S}}$(P31, P32, P33, P34, P35, P36, P37).