jsl-decora.Blend.jsl Maven / Gradle / Ivy
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<<
private float getOpacity() {
return getEffect().getOpacity();
}
>>
param sampler botImg;
param sampler topImg;
param float opacity;
//
// All blend modes are based on the same equations:
//
// Ra = Ba + Ta - Ba x Ta
// Ra x Rc' = [(1 - Ta) x Ba x Bc'] + [(1 - Ba) x Ta x Tc'] + Ba x Ta x B(Bc', Tc')
//
// where
//
// Ba = bottom alpha
// Bc' = bottom non-premultiplied color
// Ta = top alpha
// Tc' = top non-premultiplied color
// Ra = result alpha
// Rc' = result non-premultiplied color
// B(Bc', Tc') = blend mode equation
//
// If the colors are premultiplied then the second equation becomes
//
// Rc = [(1 - Ta) x Bc] + [(1 - Ba) x Tc] + Ba x Ta x B(Bc / Ba, Tc / Ta)
//
// where
//
// Bc = bottom premultiplied color
// Tc = top premultiplied color
// Rc = result premultiplied color
//
// For a given mode the final equation is therefore derived from the blend
// mode equation applied to the premultiplied colors and substituted in the
// above equation for Rc.
//
// Reference:
// PDF Reference, sixth edition, Adobe Portable Document Format, Version 1.7,
// November 2006, section 7.2.
//
// placeholder for blend_() function
%s
void main()
{
float4 bot = sample(botImg, pos0);
float4 top = sample(topImg, pos1) * opacity;
color = blend_%s(bot, top);
}