werror()

Error

Appendix Image.Layer modes

All channels are calculated separately, if nothing else is specified.

top layer
bottom layer
normal		D=L applied with alpha: D=(L*aL+S*(1-aL)*aS) / (aL+(1-aL)*aS), aD=(aL+(1-aL)*aS)
add		D=L+S applied with alpha, aD=aS
subtract		D=S-L applied with alpha, aD=aS
multiply		D=S*L applied with alpha, aD=aS
divide		D=S/L applied with alpha, aD=aS
negdivide		D=1.0-S/L applied with alpha, aD=aS
modulo		D=S%L applied with alpha, aD=aS
invsubtract		D=L-S applied with alpha, aD=aS
invdivide		D=L/S applied with alpha, aD=aS
invmodulo		D=L%S applied with alpha, aD=aS
imultiply		D=(1-L)*S applied with alpha, aD=aS
idivide		D=S/(1-L) applied with alpha, aD=aS
invidivide		D=L/(1-S) applied with alpha, aD=aS
difference		D=abs(L-S) applied with alpha, aD=aS
max		D=max(L,S) applied with alpha, aD=aS
min		D=min(L,S) applied with alpha, aD=aS
bitwise_and		D=L&S applied with alpha, aD=aS
bitwise_or		D=L|S applied with alpha, aD=aS
bitwise_xor		D=L^S applied with alpha, aD=aS
replace		D=(L*aL+S*(1-aL)*aS) / (aL+(1-aL)*aS), aD=aS
red		Dr=(Lr*aLr+Sr*(1-aLr)*aSr) / (aLr+(1-aLr)*aSr), Dgb=Sgb, aD=aS
green		Dg=(Lg*aLg+Sg*(1-aLg)*aSg) / (aLg+(1-aLg)*aSg), Drb=Srb, aD=aS
blue		Db=(Lb*aLb+Sb*(1-aLb)*aSb) / (aLb+(1-aLb)*aSb), Drg=Srg, aD=aS
hardlight		Like photoshop hardlight layer mode, aD=aS
replace_hsv		Dhsv=Lhsv apply with alpha, aD=aS
hue		Dh=Lh apply with alpha, Dsv=Lsv, aD=aS
saturation		Ds=Ls apply with alpha, Dhv=Lhv, aD=aS
value		Dv=Lv apply with alpha, Dhs=Lhs, aD=aS
color		Dhs=Lhs apply with alpha, Dv=Lv, aD=aS
value_mul		Dv=Lv*Sv apply with alpha, Dhs=Lhs, aD=aS
darken		Dv=min(Lv,Sv) apply with alpha, Dhs=Lhs, aD=aS
lighten		Dv=max(Lv,Sv) apply with alpha, Dhs=Lhs, aD=aS
saturate		Ds=max(Ls,Ss) apply with alpha, Dhv=Lhv, aD=aS
desaturate		Ds=min(Ls,Ss) apply with alpha, Dhv=Lhv, aD=aS
hls_replace		Dhls=Lhls apply with alpha, aD=aS
hls_hue		Dh=Lh apply with alpha, Dsv=Lsv, aD=aS
hls_saturation		Ds=Ls apply with alpha, Dhv=Lhv, aD=aS
hls_lightness		Dl=Ll apply with alpha, Dhs=Lhs, aD=aS
hls_color		Dhs=Lhs apply with alpha, Dl=Ll, aD=aS
hls_lightness_mul		Dl=Ll*Sl apply with alpha, Dhs=Lhs, aD=aS
hls_darken		Dl=min(Ll,Sl) apply with alpha, Dhs=Lhs, aD=aS
hls_lighten		Dl=max(Ll,Sl) apply with alpha, Dhs=Lhs, aD=aS
hls_saturate		Ds=max(Ls,Ss) apply with alpha, Dhl=Lhl, aD=aS
hls_desaturate		Ds=min(Ls,Ss) apply with alpha, Dhl=Lhl, aD=aS
dissolve		i=random 0 or 1, D=i?L:S, aD=i+aS
behind		D=(S*aS+L*(1-aS)*aL) / (aS+(1-aS)*aL), aD=(aS+(1-aS)*aL); simply swap S and L
erase		D=S, aD=aS*(1-aL)
screen		1-(1-S)*(1-L) applied with alpha, aD=aS
overlay		(1-(1-a)*(1-b)-a*b)*a+a*b applied with alpha, aD=aS
burn_alpha		aD=aL+aS applied with alpha, D=L+S; experimental, may change or be removed
equal		each channel D=max if L==S, 0 otherwise, apply with alpha
not_equal		each channel D=max if L!=S, 0 otherwise, apply with alpha
less		each channel D=max if L<S, 0 otherwise, apply with alpha
more		each channel D=max if L>S, 0 otherwise, apply with alpha
less_or_equal		each channel D=max if L<=S, 0 otherwise, apply with alpha
more_or_equal		each channel D=max if L>=S, 0 otherwise, apply with alpha
logic_equal		logic: D=white and opaque if L==S, black and transparent otherwise
logic_not_equal		logic: D=white and opaque if any L!=S, black and transparent otherwise
logic_strict_less		logic: D=white and opaque if all L<S, black and transparent otherwise
logic_strict_more		logic: D=white and opaque if all L>S, black and transparent otherwise
logic_strict_less_equal		logic: D=white and opaque if all L<=L, black and transparent otherwise
logic_strict_more_equal		logic: D=white and opaque if all L>=L, black and transparent otherwise

Extracted from Pike v7.3 release 11 at 2001-11-03.