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Minor changes in rgba_blender_normal() function

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David Capello 2017-07-18 17:05:33 -03:00
parent 7cbf5fd420
commit dd3ce20133
1 changed files with 20 additions and 16 deletions
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36
src/doc/blend_funcs.cpp
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@ -169,25 +169,29 @@ color_t rgba_blender_normal(color_t backdrop, color_t src, int opacity)
return backdrop;
}
int Br, Bg, Bb, Ba;
int Sr, Sg, Sb, Sa;
int Rr, Rg, Rb, Ra;
const int Br = rgba_getr(backdrop);
const int Bg = rgba_getg(backdrop);
const int Bb = rgba_getb(backdrop);
const int Ba = rgba_geta(backdrop);
Br = rgba_getr(backdrop);
Bg = rgba_getg(backdrop);
Bb = rgba_getb(backdrop);
Ba = rgba_geta(backdrop);
Sr = rgba_getr(src);
Sg = rgba_getg(src);
Sb = rgba_getb(src);
Sa = rgba_geta(src);
const int Sr = rgba_getr(src);
const int Sg = rgba_getg(src);
const int Sb = rgba_getb(src);
int Sa = rgba_geta(src);
Sa = MUL_UN8(Sa, opacity, t);
Ra = Ba + Sa - MUL_UN8(Ba, Sa, t);
Rr = Br + (Sr-Br) * Sa / Ra;
Rg = Bg + (Sg-Bg) * Sa / Ra;
Rb = Bb + (Sb-Bb) * Sa / Ra;
// Ra = Sa + Ba*(1-Sa)
// = Sa + Ba - Ba*Sa
// = Ba + Sa - Ba*Sa
// Rc = Sc*Sa/Ra + Bc*(1-Sa/Ra)
// = Sc*Sa/Ra + Bc - Bc*Sa/Ra
// = Bc + Sc*Sa/Ra - Bc*Sa/Ra
// = Bc + (Sc-Bc)*Sa/Ra
const int Ra = Ba + Sa - MUL_UN8(Ba, Sa, t);
const int Rr = Br + (Sr-Br) * Sa / Ra;
const int Rg = Bg + (Sg-Bg) * Sa / Ra;
const int Rb = Bb + (Sb-Bb) * Sa / Ra;
return rgba(Rr, Rg, Rb, Ra);
}