Add luminance mask transfer modes.

src/core/SkXfermode.cpp

Index: src/core/SkXfermode.cpp
diff --git a/src/core/SkXfermode.cpp b/src/core/SkXfermode.cpp
index 587b0b98aa433bf787843ce51172501b1138ac36..d9be8dc2680db54da81b9ff5d7423e76f4d16e37 100644
--- a/src/core/SkXfermode.cpp
+++ b/src/core/SkXfermode.cpp
@@ -632,6 +632,20 @@ static SkPMColor luminosity_modeproc(SkPMColor src, SkPMColor dst) {
 }
 
 
+static SkPMColor srcinlum_modeproc(SkPMColor src, SkPMColor dst) {
+    int luma = SkComputeLuminance(SkGetPackedR32(dst),
+                                  SkGetPackedG32(dst),
+                                  SkGetPackedB32(dst));
+    return SkAlphaMulQ(src, SkAlpha255To256(luma));
+}
+
+static SkPMColor dstinlum_modeproc(SkPMColor src, SkPMColor dst) {
+    int luma = SkComputeLuminance(SkGetPackedR32(src),
+                                  SkGetPackedG32(src),
+                                  SkGetPackedB32(src));
+    return SkAlphaMulQ(dst, SkAlpha255To256(luma));
+}
+
 struct ProcCoeff {
     SkXfermodeProc      fProc;
     SkXfermode::Coeff   fSC;
@@ -671,6 +685,8 @@ static const ProcCoeff gProcCoeffs[] = {
     { saturation_modeproc,  CANNOT_USE_COEFF,       CANNOT_USE_COEFF },
     { color_modeproc,       CANNOT_USE_COEFF,       CANNOT_USE_COEFF },
     { luminosity_modeproc,  CANNOT_USE_COEFF,       CANNOT_USE_COEFF },
+    { srcinlum_modeproc,    CANNOT_USE_COEFF,       CANNOT_USE_COEFF },
+    { dstinlum_modeproc,    CANNOT_USE_COEFF,       CANNOT_USE_COEFF },
 };
 
 ///////////////////////////////////////////////////////////////////////////////
@@ -1084,6 +1100,24 @@ public:
                                            outputColor, inputColor, dstColor, dstColor, inputColor);
                     break;
                 }
+                case SkXfermode::kSrcInLum_Mode: {
+                    builder->fsCodeAppendf("\t\tfloat luma = dot(vec3(%f, %f, %f), %s.rgb);\n",
+                                           SK_ITU_BT709_LUM_COEFF_R,
+                                           SK_ITU_BT709_LUM_COEFF_G,
+                                           SK_ITU_BT709_LUM_COEFF_B,
+                                           dstColor);
+                    builder->fsCodeAppendf("\t\t%s = %s * luma;\n", outputColor, inputColor);
+                    break;
+                }
+                case SkXfermode::kDstInLum_Mode: {
+                    builder->fsCodeAppendf("\t\tfloat luma = dot(vec3(%f, %f, %f), %s.rgb);\n",
+                                       SK_ITU_BT709_LUM_COEFF_R,
+                                       SK_ITU_BT709_LUM_COEFF_G,
+                                       SK_ITU_BT709_LUM_COEFF_B,
+                                       inputColor);
+                    builder->fsCodeAppendf("\t\t%s = %s * luma;\n", outputColor, dstColor);
+                    break;
+                }
                 default:
                     GrCrash("Unknown XferEffect mode.");
                     break;
@@ -1467,7 +1501,8 @@ const char* SkXfermode::ModeName(Mode mode) {
         "SrcOut", "DstOut", "SrcATop", "DstATop", "Xor", "Plus",
         "Modulate", "Screen", "Overlay", "Darken", "Lighten", "ColorDodge",
         "ColorBurn", "HardLight", "SoftLight", "Difference", "Exclusion",
-        "Multiply", "Hue", "Saturation", "Color",  "Luminosity"
+        "Multiply", "Hue", "Saturation", "Color",  "Luminosity", "SrcInLum",
+        "DstInLum"
     };
     return gModeStrings[mode];
     SK_COMPILE_ASSERT(SK_ARRAY_COUNT(gModeStrings) == kLastMode + 1, mode_count);