add ADD xfermode
safely handle (don't draw) if the size of SkMask exceeds 31bits
git-svn-id: http://skia.googlecode.com/svn/trunk@159 2bbb7eff-a529-9590-31e7-b0007b416f81
diff --git a/src/core/SkXfermode.cpp b/src/core/SkXfermode.cpp
index 7c336c2..9514bfa 100644
--- a/src/core/SkXfermode.cpp
+++ b/src/core/SkXfermode.cpp
@@ -45,6 +45,16 @@
}
#endif
+static unsigned saturated_add(unsigned a, unsigned b) {
+ SkASSERT(a <= 255);
+ SkASSERT(b <= 255);
+ unsigned sum = a + b;
+ if (sum > 255) {
+ sum = 255;
+ }
+ return sum;
+}
+
///////////////////////////////////////////////////////////////////////////////
bool SkXfermode::asCoeff(Coeff* src, Coeff* dst) {
@@ -500,6 +510,14 @@
return SkPackARGB32(a, r, g, b);
}
+static SkPMColor add_modeproc(SkPMColor src, SkPMColor dst) {
+ unsigned a = saturated_add(SkGetPackedA32(src), SkGetPackedA32(dst));
+ unsigned r = saturated_add(SkGetPackedR32(src), SkGetPackedR32(dst));
+ unsigned g = saturated_add(SkGetPackedG32(src), SkGetPackedG32(dst));
+ unsigned b = saturated_add(SkGetPackedB32(src), SkGetPackedB32(dst));
+ return SkPackARGB32(a, r, g, b);
+}
+
///////////////////////////////////////////////////////////////////////////////
class SkClearXfermode : public SkProcCoeffXfermode {
@@ -701,6 +719,8 @@
SkXfermode::Coeff fDC;
};
+#define CANNOT_USE_COEFF SkXfermode::Coeff(-1)
+
static const ProcCoeff gProcCoeffs[] = {
{ clear_modeproc, SkXfermode::kZero_Coeff, SkXfermode::kZero_Coeff },
{ src_modeproc, SkXfermode::kOne_Coeff, SkXfermode::kZero_Coeff },
@@ -714,12 +734,11 @@
{ srcatop_modeproc, SkXfermode::kDA_Coeff, SkXfermode::kISA_Coeff },
{ dstatop_modeproc, SkXfermode::kIDA_Coeff, SkXfermode::kSA_Coeff },
{ xor_modeproc, SkXfermode::kIDA_Coeff, SkXfermode::kISA_Coeff },
- // these two can't be represented as coefficients
- { darken_modeproc, SkXfermode::Coeff(-1), SkXfermode::Coeff(-1) },
- { lighten_modeproc, SkXfermode::Coeff(-1), SkXfermode::Coeff(-1) },
- // these can use coefficients
+ { darken_modeproc, CANNOT_USE_COEFF, CANNOT_USE_COEFF },
+ { lighten_modeproc, CANNOT_USE_COEFF, CANNOT_USE_COEFF },
{ mult_modeproc, SkXfermode::kZero_Coeff, SkXfermode::kSC_Coeff },
- { screen_modeproc, SkXfermode::kOne_Coeff, SkXfermode::kISC_Coeff }
+ { screen_modeproc, SkXfermode::kOne_Coeff, SkXfermode::kISC_Coeff },
+ { add_modeproc, CANNOT_USE_COEFF, CANNOT_USE_COEFF }
};
SkXfermode* SkPorterDuff::CreateXfermode(SkPorterDuff::Mode mode) {