| 1 |
{ RCSid $Id: cielab.cal,v 1.2 2005/05/25 04:44:25 greg Exp $ } |
| 2 |
{ |
| 3 |
Compute Lab color space and color differences from XYZ primaries. |
| 4 |
|
| 5 |
5/25/02 G.Ward |
| 6 |
} |
| 7 |
Xw = 1; Yw = 1; Zw = 1; { default white } |
| 8 |
sq(x) : x*x; |
| 9 |
DEL : 6/29; |
| 10 |
bfunc(x) : if(x - DEL*DEL*DEL, x^(1/3), x/(3*DEL*DEL) + 2/3*DEL); |
| 11 |
Ls(Yi) : 116*bfunc(Yi/Yw) - 16; |
| 12 |
as(Xi,Yi,Zi) : 500*(bfunc(Xi/Xw) - bfunc(Yi/Yw)); |
| 13 |
bs(Xi,Yi,Zi) : 200*(bfunc(Yi/Yw) - bfunc(Zi/Zw)); |
| 14 |
|
| 15 |
{ CIE 1976 Lab delta E formula } |
| 16 |
dE76(X1,Y1,Z1,X2,Y2,Z2) : sqrt( sq(Ls(Y1)-Ls(Y2)) |
| 17 |
+ sq(as(X1,Y1,Z1)-as(X2,Y2,Z2)) |
| 18 |
+ sq(bs(X1,Y1,Z1)-bs(X2,Y2,Z2)) ); |
| 19 |
|
| 20 |
{ CIE 1994 Lab delta E formula } |
| 21 |
kL = 1; kC = 1; kH = 1; { viewing factors } |
| 22 |
Cs(Xi,Yi,Zi) : sqrt( sq(as(Xi,Yi,Zi)) + sq(bs(Xi,Yi,Zi)) ); |
| 23 |
C1s(X1,Y1,Z1,X2,Y2,Z2) : sqrt(Cs(X1,Y1,Z1)*Cs(X2,Y2,Z2)); |
| 24 |
dHs(X1,Y1,Z1,X2,Y2,Z2) : sqrt( sq(as(X1,Y1,Z1)-as(X2,Y2,Z2)) |
| 25 |
+ sq(bs(X1,Y1,Z1)-bs(X2,Y2,Z2)) |
| 26 |
- sq(Cs(X1,Y1,Z1)-Cs(X2,Y2,Z2)) ); |
| 27 |
dE94(X1,Y1,Z1,X2,Y2,Z2) : sqrt( sq((Ls(X1,Y1,Z1)-Ls(X2,Y2,Z2))/kL) |
| 28 |
+ sq( (Cs(X1,Y1,Z1)-Cs(X2,Y2,Z2)) / |
| 29 |
(kC*(1+.048*C1s(X1,Y1,Z1,X2,Y2,Z2))) ) |
| 30 |
+ sq( dHs(X1,Y1,Z1,X2,Y2,Z2) / |
| 31 |
(kH*(1+.014*C1s(X1,Y1,Z1,X2,Y2,Z2))) ) ) |
