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Bug 1294614 - Part 3: Add DiluteColor(). r=dholbert.

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MozReview-Commit-ID: AKfVLgeN9ZO

--HG--
extra : rebase_source : a0558b6e25d955956d54acac1d51387a1de76db5
This commit is contained in:
Hiroyuki Ikezoe 2016-08-25 09:27:42 +09:00
parent aeeaf198d9
commit c8b48f39ce
1 changed files with 38 additions and 2 deletions
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40
layout/style/StyleAnimationValue.cpp
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@ -1196,6 +1196,32 @@ AddWeightedColors(double aCoeff1, nscolor aColor1,
return NS_RGBA(Rres, Gres, Bres, Ares);
}
// Multiplies |aColor| by |aDilutionRatio| with premultiplication.
// (The logic here should pretty closely match AddWeightedColors()' logic.)
static nscolor
DiluteColor(nscolor aColor, double aDilutionRatio)
{
MOZ_ASSERT(aDilutionRatio >= 0.0 && aDilutionRatio <= 1.0,
"Dilution ratio should be in [0, 1]");
double A = NS_GET_A(aColor) * (1.0 / 255.0);
double Aresf = A * aDilutionRatio;
if (Aresf <= 0.0) {
return NS_RGBA(0, 0, 0, 0);
}
// Premultiplication
double R = NS_GET_R(aColor) * A;
double G = NS_GET_G(aColor) * A;
double B = NS_GET_B(aColor) * A;
double factor = 1.0 / Aresf;
return NS_RGBA(ClampColor(R * aDilutionRatio * factor),
ClampColor(G * aDilutionRatio * factor),
ClampColor(B * aDilutionRatio * factor),
NSToIntRound(Aresf * 255.0));
}
static bool
AddShadowItems(double aCoeff1, const nsCSSValue &aValue1,
double aCoeff2, const nsCSSValue &aValue2,
@ -2384,8 +2410,18 @@ StyleAnimationValue::AddWeighted(nsCSSPropertyID aProperty,
case eUnit_Color: {
nscolor color1 = aValue1.GetColorValue();
nscolor color2 = aValue2.GetColorValue();
nscolor resultColor =
AddWeightedColors(aCoeff1, color1, aCoeff2, color2);
nscolor resultColor;
// We are using AddWeighted() with a zero aCoeff2 for colors to
// pretend AddWeighted() against transparent color, i.e. rgba(0, 0, 0, 0).
// But unpremultiplication in AddWeightedColors() does not work well
// for such cases, so we use another function named DiluteColor() which
// has a similar logic to AddWeightedColors().
if (aCoeff2 == 0.0) {
resultColor = DiluteColor(color1, aCoeff1);
} else {
resultColor = AddWeightedColors(aCoeff1, color1, aCoeff2, color2);
}
aResultValue.SetColorValue(resultColor);
return true;
}