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{ RCSid $Id: cieluv.cal,v 1.3 2015/06/18 00:11:39 greg Exp $ } |
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{ |
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Compute Luv color space and color differences from XYZ primaries. |
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|
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5/4/98 G.W.Larson |
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} |
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Xw = 1; Yw = 1; Zw = 1; { default white } |
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sq(x) : x*x; |
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up(Xi,Yi,Zi) : 4*Xi/(Xi + 15*Yi + 3*Zi); |
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vp(Xi,Yi,Zi) : 9*Yi/(Xi + 15*Yi + 3*Zi); |
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up_neu : up(1,1,1); |
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vp_neu : vp(1,1,1); |
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uw = up(Xw,Yw,Zw); |
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vw = vp(Xw,Yw,Zw); |
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Ls(Yi) = if(Yi/Yw - .01, 116*(Yi/Yw)^(1/3) - 16, 903.3*Yi/Yw); |
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us(Xi,Yi,Zi) = 13*Ls(Yi)*(up(Xi,Yi,Zi) - uw); |
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vs(Xi,Yi,Zi) = 13*Ls(Yi)*(vp(Xi,Yi,Zi) - vw); |
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hue_deg(Xi,Yi,Zi) = 180/PI*atan2(vs(Xi,Yi,Zi),us(Xi,Yi,Zi)); |
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sat_uv(Xi,Yi,Zi) = 13*sqrt(sq(up(Xi,Yi,Zi)-uw) + sq(vp(Xi,Yi,Zi)-vw)); |
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dE(X1,Y1,Z1,X2,Y2,Z2) = sqrt(sq(Ls(Y1)-Ls(Y2)) + sq(us(X1,Y1,Z1)-us(X2,Y2,Z2)) |
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+ sq(vs(X1,Y1,Z1)-vs(X2,Y2,Z2))); |
