index	eq	band
NR	R/(R+G+B)	C
NG	G/(R+G+B)	C
NB	B/(R+G+B)	C
BI	sqrt((R^2+G^2+B^2)/3)	C
BIM	sqrt((R*2+G*2+B*2)/3)	C
SCI	(R-G)/(R+G)	C
GLI	(2*G-R-B)/(2*G+R+B)	C
HI	(2*R-G-B)/(G-B)	C
NGRDI	(G-R)/(G+R)	C
SI	(R-B)/(R+B)	C
VARI	(G-R)/(G+R-B)	C
HUE	atan(2*(B-G-R)/30.5*(G-R))	C
BGI	B/G	C
