Add luminance mask transfer modes.

This adds kSrcInLum_Mode and kDstInLum_Mode, to support CSS and SVG luminance masks (http://www.w3.org/TR/css-masking/#MaskValues , http://www.w3.org/TR/SVG/masking.html#Masking ).

The transfer coefficient is computed according to http://www.w3.org/TR/2011/REC-SVG11-20110816/filters.html#feColorMatrixElement "luminance-to-alpha":

  luma = 0.2125 * r + 0.7154 * g + 0.0721 * b


R=bsalomon@google.com, reed@google.com, robertphillips@google.com, vandebo@chromium.org

Author: fmalita@chromium.org

Review URL: https://chromiumcodereview.appspot.com/22918012

git-svn-id: http://skia.googlecode.com/svn/trunk@10887 2bbb7eff-a529-9590-31e7-b0007b416f81
diff --git a/bench/XfermodeBench.cpp b/bench/XfermodeBench.cpp
index 0d85fef..71cf0e6 100644
--- a/bench/XfermodeBench.cpp
+++ b/bench/XfermodeBench.cpp
@@ -12,6 +12,7 @@
 #include "SkRandom.h"
 #include "SkString.h"
 #include "SkXfermode.h"
+#include "SkLumaXfermode.h"
 
 // Benchmark that draws non-AA rects with an SkXfermode::Mode
 class XfermodeBench : public SkBenchmark {
@@ -22,6 +23,13 @@
         fName.printf("Xfermode_%s", SkXfermode::ModeName(mode));
     }
 
+    XfermodeBench(void* param, SkXfermode* xferMode, const char* name)
+        : SkBenchmark(param) {
+        SkASSERT(NULL != xferMode);
+        fXfermode.reset(xferMode);
+        fName.printf("Xfermode_%s", name);
+    }
+
 protected:
     virtual const char* onGetName() SK_OVERRIDE { return fName.c_str(); }
 
@@ -58,62 +66,44 @@
 
 //////////////////////////////////////////////////////////////////////////////
 
-static SkBenchmark* Fact00(void* p) { return new XfermodeBench(p, SkXfermode::kClear_Mode); }
-static SkBenchmark* Fact01(void* p) { return new XfermodeBench(p, SkXfermode::kSrc_Mode); }
-static SkBenchmark* Fact02(void* p) { return new XfermodeBench(p, SkXfermode::kDst_Mode); }
-static SkBenchmark* Fact03(void* p) { return new XfermodeBench(p, SkXfermode::kSrcOver_Mode); }
-static SkBenchmark* Fact04(void* p) { return new XfermodeBench(p, SkXfermode::kDstOver_Mode); }
-static SkBenchmark* Fact05(void* p) { return new XfermodeBench(p, SkXfermode::kSrcIn_Mode); }
-static SkBenchmark* Fact06(void* p) { return new XfermodeBench(p, SkXfermode::kDstIn_Mode); }
-static SkBenchmark* Fact07(void* p) { return new XfermodeBench(p, SkXfermode::kSrcOut_Mode); }
-static SkBenchmark* Fact08(void* p) { return new XfermodeBench(p, SkXfermode::kDstOut_Mode); }
-static SkBenchmark* Fact09(void* p) { return new XfermodeBench(p, SkXfermode::kSrcATop_Mode); }
-static SkBenchmark* Fact10(void* p) { return new XfermodeBench(p, SkXfermode::kDstATop_Mode); }
-static SkBenchmark* Fact11(void* p) { return new XfermodeBench(p, SkXfermode::kXor_Mode); }
-static SkBenchmark* Fact12(void* p) { return new XfermodeBench(p, SkXfermode::kPlus_Mode); }
-static SkBenchmark* Fact13(void* p) { return new XfermodeBench(p, SkXfermode::kModulate_Mode); }
-static SkBenchmark* Fact14(void* p) { return new XfermodeBench(p, SkXfermode::kScreen_Mode); }
-static SkBenchmark* Fact15(void* p) { return new XfermodeBench(p, SkXfermode::kOverlay_Mode); }
-static SkBenchmark* Fact16(void* p) { return new XfermodeBench(p, SkXfermode::kDarken_Mode); }
-static SkBenchmark* Fact17(void* p) { return new XfermodeBench(p, SkXfermode::kLighten_Mode); }
-static SkBenchmark* Fact18(void* p) { return new XfermodeBench(p, SkXfermode::kColorDodge_Mode); }
-static SkBenchmark* Fact19(void* p) { return new XfermodeBench(p, SkXfermode::kColorBurn_Mode); }
-static SkBenchmark* Fact20(void* p) { return new XfermodeBench(p, SkXfermode::kHardLight_Mode); }
-static SkBenchmark* Fact21(void* p) { return new XfermodeBench(p, SkXfermode::kSoftLight_Mode); }
-static SkBenchmark* Fact22(void* p) { return new XfermodeBench(p, SkXfermode::kDifference_Mode); }
-static SkBenchmark* Fact23(void* p) { return new XfermodeBench(p, SkXfermode::kExclusion_Mode); }
-static SkBenchmark* Fact24(void* p) { return new XfermodeBench(p, SkXfermode::kMultiply_Mode); }
-static SkBenchmark* Fact25(void* p) { return new XfermodeBench(p, SkXfermode::kHue_Mode); }
-static SkBenchmark* Fact26(void* p) { return new XfermodeBench(p, SkXfermode::kSaturation_Mode); }
-static SkBenchmark* Fact27(void* p) { return new XfermodeBench(p, SkXfermode::kColor_Mode); }
-static SkBenchmark* Fact28(void* p) { return new XfermodeBench(p, SkXfermode::kLuminosity_Mode); }
+#define CONCAT_I(x, y) x ## y
+#define CONCAT(x, y) CONCAT_I(x, y) // allow for macro expansion
+#define BENCH(...) \
+    static SkBenchmark* CONCAT(Fact, __LINE__)(void *p) { return new XfermodeBench(p, __VA_ARGS__); };\
+    static BenchRegistry CONCAT(gReg, __LINE__)(CONCAT(Fact, __LINE__));
 
-static BenchRegistry gReg00(Fact00);
-static BenchRegistry gReg01(Fact01);
-static BenchRegistry gReg02(Fact02);
-static BenchRegistry gReg03(Fact03);
-static BenchRegistry gReg04(Fact04);
-static BenchRegistry gReg05(Fact05);
-static BenchRegistry gReg06(Fact06);
-static BenchRegistry gReg07(Fact07);
-static BenchRegistry gReg08(Fact08);
-static BenchRegistry gReg09(Fact09);
-static BenchRegistry gReg10(Fact10);
-static BenchRegistry gReg11(Fact11);
-static BenchRegistry gReg12(Fact12);
-static BenchRegistry gReg13(Fact13);
-static BenchRegistry gReg14(Fact14);
-static BenchRegistry gReg15(Fact15);
-static BenchRegistry gReg16(Fact16);
-static BenchRegistry gReg17(Fact17);
-static BenchRegistry gReg18(Fact18);
-static BenchRegistry gReg19(Fact19);
-static BenchRegistry gReg20(Fact20);
-static BenchRegistry gReg21(Fact21);
-static BenchRegistry gReg22(Fact22);
-static BenchRegistry gReg23(Fact23);
-static BenchRegistry gReg24(Fact24);
-static BenchRegistry gReg25(Fact25);
-static BenchRegistry gReg26(Fact26);
-static BenchRegistry gReg27(Fact27);
-static BenchRegistry gReg28(Fact28);
+BENCH(SkXfermode::kClear_Mode)
+BENCH(SkXfermode::kSrc_Mode)
+BENCH(SkXfermode::kDst_Mode)
+BENCH(SkXfermode::kSrcOver_Mode)
+BENCH(SkXfermode::kDstOver_Mode)
+BENCH(SkXfermode::kSrcIn_Mode)
+BENCH(SkXfermode::kDstIn_Mode)
+BENCH(SkXfermode::kSrcOut_Mode)
+BENCH(SkXfermode::kDstOut_Mode)
+BENCH(SkXfermode::kSrcATop_Mode)
+BENCH(SkXfermode::kDstATop_Mode)
+BENCH(SkXfermode::kXor_Mode)
+
+BENCH(SkXfermode::kPlus_Mode)
+BENCH(SkXfermode::kModulate_Mode)
+BENCH(SkXfermode::kScreen_Mode)
+
+BENCH(SkXfermode::kOverlay_Mode)
+BENCH(SkXfermode::kDarken_Mode)
+BENCH(SkXfermode::kLighten_Mode)
+BENCH(SkXfermode::kColorDodge_Mode)
+BENCH(SkXfermode::kColorBurn_Mode)
+BENCH(SkXfermode::kHardLight_Mode)
+BENCH(SkXfermode::kSoftLight_Mode)
+BENCH(SkXfermode::kDifference_Mode)
+BENCH(SkXfermode::kExclusion_Mode)
+BENCH(SkXfermode::kMultiply_Mode)
+
+BENCH(SkXfermode::kHue_Mode)
+BENCH(SkXfermode::kSaturation_Mode)
+BENCH(SkXfermode::kColor_Mode)
+BENCH(SkXfermode::kLuminosity_Mode)
+
+BENCH(SkLumaMaskXfermode::Create(SkXfermode::kSrcIn_Mode), "SrcInLuma")
+BENCH(SkLumaMaskXfermode::Create(SkXfermode::kDstIn_Mode), "DstInLuma")
diff --git a/gm/lumamode.cpp b/gm/lumamode.cpp
new file mode 100644
index 0000000..ddafc7c
--- /dev/null
+++ b/gm/lumamode.cpp
@@ -0,0 +1,86 @@
+/*
+ * Copyright 2013 Google Inc.
+ *
+ * Use of this source code is governed by a BSD-style license that can be
+ * found in the LICENSE file.
+ */
+
+#include "gm.h"
+#include "SkCanvas.h"
+#include "SkLumaXfermode.h"
+
+static void show_scene(SkCanvas* canvas, SkXfermode* mode, const char* label) {
+    SkPaint paint;
+    paint.setAntiAlias(true);
+    SkRect r, c, bounds = { 10, 10, 110, 110 };
+
+    c = bounds;
+    c.fRight = bounds.centerX();
+    r = bounds;
+    r.fBottom = bounds.centerY();
+    canvas->drawRect(r, paint);
+
+    SkScalar tw = paint.measureText(label, strlen(label));
+    canvas->drawText(label, strlen(label), bounds.centerX() - tw / 2,
+                     bounds.bottom() + 15, paint);
+
+    canvas->saveLayer(&bounds, NULL);
+
+    r = bounds;
+    r.inset(20, 0);
+    paint.setColor(0x80FFFF00);
+    canvas->drawOval(r, paint);
+    canvas->save();
+    canvas->clipRect(c);
+    paint.setColor(0xFFFFFF00);
+    canvas->drawOval(r, paint);
+    canvas->restore();
+
+    SkPaint xferPaint;
+    xferPaint.setXfermode(mode);
+    canvas->saveLayer(&bounds, &xferPaint);
+
+    r = bounds;
+    r.inset(0, 20);
+    paint.setColor(0x8080FF00);
+    canvas->drawOval(r, paint);
+    canvas->save();
+    canvas->clipRect(c);
+    paint.setColor(0xFF80FF00);
+    canvas->drawOval(r, paint);
+    canvas->restore();
+
+    canvas->restore();
+    canvas->restore();
+}
+
+class LumaXfermodeGM : public skiagm::GM {
+public:
+    LumaXfermodeGM() {}
+
+protected:
+    virtual SkString onShortName() SK_OVERRIDE {
+        return SkString("lumamode");
+    }
+
+    virtual SkISize onISize() SK_OVERRIDE {
+        return SkISize::Make(450, 140);
+    }
+
+    virtual void onDraw(SkCanvas* canvas) SK_OVERRIDE {
+        show_scene(canvas, NULL, "SrcOver");
+        canvas->translate(150, 0);
+        SkAutoTUnref<SkXfermode> src_in(SkLumaMaskXfermode::Create(SkXfermode::kSrcIn_Mode));
+        show_scene(canvas, src_in.get(), "SrcInLuma");
+        canvas->translate(150, 0);
+        SkAutoTUnref<SkXfermode> dst_in(SkLumaMaskXfermode::Create(SkXfermode::kDstIn_Mode));
+        show_scene(canvas, dst_in.get(), "DstInLuma");
+    }
+
+private:
+    typedef skiagm::GM INHERITED;
+};
+
+//////////////////////////////////////////////////////////////////////////////
+
+DEF_GM( return SkNEW(LumaXfermodeGM); )
diff --git a/gyp/effects.gypi b/gyp/effects.gypi
index 84d38ac..56ba59f 100644
--- a/gyp/effects.gypi
+++ b/gyp/effects.gypi
@@ -39,6 +39,7 @@
     '<(skia_src_path)/effects/SkLayerRasterizer.cpp',
     '<(skia_src_path)/effects/SkLerpXfermode.cpp',
     '<(skia_src_path)/effects/SkLightingImageFilter.cpp',
+    '<(skia_src_path)/effects/SkLumaXfermode.cpp',
     '<(skia_src_path)/effects/SkMagnifierImageFilter.cpp',
     '<(skia_src_path)/effects/SkMatrixConvolutionImageFilter.cpp',
     '<(skia_src_path)/effects/SkMergeImageFilter.cpp',
@@ -99,6 +100,7 @@
     '<(skia_include_path)/effects/SkLayerRasterizer.h',
     '<(skia_include_path)/effects/SkLerpXfermode.h',
     '<(skia_include_path)/effects/SkLightingImageFilter.h',
+    '<(skia_include_path)/effects/SkLumaXfermode.h',
     '<(skia_include_path)/effects/SkOffsetImageFilter.h',
     '<(skia_include_path)/effects/SkMorphologyImageFilter.h',
     '<(skia_include_path)/effects/SkPaintFlagsDrawFilter.h',
diff --git a/gyp/gmslides.gypi b/gyp/gmslides.gypi
index 76b6739..b2afc5e 100644
--- a/gyp/gmslides.gypi
+++ b/gyp/gmslides.gypi
@@ -68,6 +68,7 @@
     '../gm/inversepaths.cpp',
     '../gm/lerpmode.cpp',
     '../gm/lighting.cpp',
+    '../gm/lumamode.cpp',
     '../gm/image.cpp',
     '../gm/imagefiltersbase.cpp',
     '../gm/imagefilterscropped.cpp',
diff --git a/gyp/public_headers.gypi b/gyp/public_headers.gypi
index 10f30e5..472fe29 100644
--- a/gyp/public_headers.gypi
+++ b/gyp/public_headers.gypi
@@ -78,6 +78,7 @@
       'effects/SkMergeImageFilter.h',
       'effects/SkPerlinNoiseShader.h',
       'effects/SkLerpXfermode.h',
+      'effects/SkLumaXfermode.h',
       'effects/SkRectShaderImageFilter.h',
       'effects/SkMagnifierImageFilter.h',
       'effects/SkBicubicImageFilter.h',
diff --git a/include/effects/SkLumaXfermode.h b/include/effects/SkLumaXfermode.h
new file mode 100644
index 0000000..5bcd10e
--- /dev/null
+++ b/include/effects/SkLumaXfermode.h
@@ -0,0 +1,58 @@
+/*
+ * Copyright 2013 Google Inc.
+ *
+ * Use of this source code is governed by a BSD-style license that can be
+ * found in the LICENSE file.
+ */
+
+#ifndef SkLumaXfermode_DEFINED
+#define SkLumaXfermode_DEFINED
+
+#include "SkXfermode.h"
+
+/**
+ *  Luminance mask transfer, as defined in
+ *  http://www.w3.org/TR/SVG/masking.html#Masking
+ *  http://www.w3.org/TR/css-masking/#MaskValues
+ *
+ *  The luminance-to-alpha function is applied before performing a standard
+ *  SrcIn/DstIn xfer:
+ *
+ *    luma(C) = (0.2125 * C.r + 0.7154 * C.g + 0.0721 * C.b) * C.a
+ *
+ *  (where C is un-premultiplied)
+ */
+class SK_API SkLumaMaskXfermode : public SkXfermode {
+public:
+    /** Return an SkLumaMaskXfermode object for the specified submode.
+     *
+     *  Only kSrcIn_Mode and kDstIn_Mode are supported - for everything else,
+     *  the factory returns NULL.
+     */
+    static SkXfermode* Create(SkXfermode::Mode);
+
+    virtual SkPMColor xferColor(SkPMColor, SkPMColor) const SK_OVERRIDE;
+    virtual void xfer32(SkPMColor dst[], const SkPMColor src[], int count,
+                        const SkAlpha aa[]) const SK_OVERRIDE;
+
+    SK_DEVELOPER_TO_STRING()
+    SK_DECLARE_PUBLIC_FLATTENABLE_DESERIALIZATION_PROCS(SkLumaMaskXfermode)
+
+#if SK_SUPPORT_GPU
+    virtual bool asNewEffectOrCoeff(GrContext*, GrEffectRef**, Coeff*, Coeff*,
+                                    GrTexture*) const SK_OVERRIDE;
+#endif
+
+protected:
+    SkLumaMaskXfermode(SkFlattenableReadBuffer&);
+    virtual void flatten(SkFlattenableWriteBuffer&) const SK_OVERRIDE;
+
+private:
+    SkLumaMaskXfermode(SkXfermode::Mode);
+
+    const SkXfermode::Mode fMode;
+
+    typedef SkXfermode INHERITED;
+};
+
+#endif
diff --git a/src/effects/SkLumaXfermode.cpp b/src/effects/SkLumaXfermode.cpp
new file mode 100644
index 0000000..df0a663
--- /dev/null
+++ b/src/effects/SkLumaXfermode.cpp
@@ -0,0 +1,221 @@
+/*
+ * Copyright 2013 Google Inc.
+ *
+ * Use of this source code is governed by a BSD-style license that can be
+ * found in the LICENSE file.
+ */
+
+#include "SkLumaXfermode.h"
+#include "SkColorPriv.h"
+#include "SkFlattenableBuffers.h"
+#include "SkString.h"
+
+#if SK_SUPPORT_GPU
+#include "gl/GrGLEffect.h"
+#include "gl/GrGLEffectMatrix.h"
+#include "GrContext.h"
+#include "GrTBackendEffectFactory.h"
+#endif
+
+static inline SkPMColor luma_proc(const SkPMColor a, const SkPMColor b) {
+    unsigned luma = SkComputeLuminance(SkGetPackedR32(b),
+                                       SkGetPackedG32(b),
+                                       SkGetPackedB32(b));
+    return SkAlphaMulQ(a, SkAlpha255To256(luma));
+}
+
+template <typename T>
+static inline const T* lumaOpA(SkXfermode::Mode mode,
+                               const T* src, const T* dst) {
+    return SkXfermode::kSrcIn_Mode == mode ? src : dst;
+}
+
+template <typename T>
+static inline const T* lumaOpB(SkXfermode::Mode mode,
+                               const T* src, const T* dst) {
+    return SkXfermode::kSrcIn_Mode == mode ? dst : src;
+}
+
+SkXfermode* SkLumaMaskXfermode::Create(SkXfermode::Mode mode) {
+    if (kSrcIn_Mode == mode || kDstIn_Mode == mode) {
+        return SkNEW_ARGS(SkLumaMaskXfermode, (mode));
+    }
+    return NULL;
+}
+
+SkLumaMaskXfermode::SkLumaMaskXfermode(SkXfermode::Mode mode)
+    : fMode(mode) {
+    SkASSERT(kSrcIn_Mode == mode || kDstIn_Mode == mode);
+}
+
+SkLumaMaskXfermode::SkLumaMaskXfermode(SkFlattenableReadBuffer& buffer)
+    : INHERITED(buffer)
+    , fMode((SkXfermode::Mode)buffer.readUInt()) {
+    SkASSERT(kSrcIn_Mode == fMode || kDstIn_Mode == fMode);
+}
+
+void SkLumaMaskXfermode::flatten(SkFlattenableWriteBuffer& buffer) const {
+    INHERITED::flatten(buffer);
+    buffer.writeUInt(fMode);
+}
+
+SkPMColor SkLumaMaskXfermode::xferColor(SkPMColor src, SkPMColor dst) const {
+    const SkPMColor* a = lumaOpA<SkPMColor>(fMode, &src, &dst);
+    const SkPMColor* b = lumaOpB<SkPMColor>(fMode, &src, &dst);
+    return luma_proc(*a, *b);
+}
+
+void SkLumaMaskXfermode::xfer32(SkPMColor dst[], const SkPMColor src[],
+                                int count, const SkAlpha aa[]) const {
+    const SkPMColor* a = lumaOpA<SkPMColor>(fMode, src, dst);
+    const SkPMColor* b = lumaOpB<SkPMColor>(fMode, src, dst);
+
+    if (aa) {
+        for (int i = 0; i < count; ++i) {
+            unsigned cov = aa[i];
+            if (cov) {
+                unsigned resC = luma_proc(a[i], b[i]);
+                if (cov < 255) {
+                    resC = SkAlphaMulQ(resC, SkAlpha255To256(cov));
+                }
+                dst[i] = resC;
+            }
+        }
+    } else {
+        for (int i = 0; i < count; ++i) {
+            dst[i] = luma_proc(a[i], b[i]);
+        }
+    }
+}
+
+#ifdef SK_DEVELOPER
+void SkLumaMaskXfermode::toString(SkString* str) const {
+    str->printf("SkLumaMaskXfermode: mode: %s",
+                fMode == kSrcIn_Mode ? "SRC_IN" : "DST_IN");
+}
+#endif
+
+#if SK_SUPPORT_GPU
+//////////////////////////////////////////////////////////////////////////////
+
+class GrGLLumaMaskEffect : public GrGLEffect {
+public:
+    GrGLLumaMaskEffect(const GrBackendEffectFactory&, const GrDrawEffect&);
+    virtual ~GrGLLumaMaskEffect();
+
+    virtual void emitCode(GrGLShaderBuilder*,
+                          const GrDrawEffect&,
+                          EffectKey,
+                          const char* outputColor,
+                          const char* inputColor,
+                          const TextureSamplerArray&) SK_OVERRIDE;
+
+    static inline EffectKey GenKey(const GrDrawEffect&, const GrGLCaps&);
+
+private:
+    typedef GrGLEffect INHERITED;
+};
+
+class GrLumaMaskEffect : public GrEffect {
+public:
+    static GrEffectRef* Create(SkXfermode::Mode mode) {
+        AutoEffectUnref effect(SkNEW_ARGS(GrLumaMaskEffect, (mode)));
+        return CreateEffectRef(effect);
+    }
+
+    virtual ~GrLumaMaskEffect();
+
+    typedef GrGLLumaMaskEffect GLEffect;
+    static const char* Name() { return "LumaMask"; }
+
+    virtual const GrBackendEffectFactory& getFactory() const SK_OVERRIDE;
+    virtual void getConstantColorComponents(GrColor*, uint32_t*) const SK_OVERRIDE;
+
+    SkXfermode::Mode getMode() const { return fMode; }
+
+private:
+    GrLumaMaskEffect(SkXfermode::Mode);
+
+    virtual bool onIsEqual(const GrEffect&) const SK_OVERRIDE;
+
+    const SkXfermode::Mode fMode;
+};
+
+//////////////////////////////////////////////////////////////////////////////
+
+GrGLLumaMaskEffect::GrGLLumaMaskEffect(const GrBackendEffectFactory& factory,
+                                       const GrDrawEffect&)
+   : INHERITED(factory) {
+}
+
+GrGLLumaMaskEffect::~GrGLLumaMaskEffect() {
+}
+
+void GrGLLumaMaskEffect::emitCode(GrGLShaderBuilder* builder,
+                                    const GrDrawEffect& effect,
+                                    EffectKey key,
+                                    const char* outputColor,
+                                    const char* inputColor,
+                                    const TextureSamplerArray& samplers) {
+
+    const GrLumaMaskEffect& lumaEffect = effect.castEffect<GrLumaMaskEffect>();
+    const char* dstColor = builder->dstColor();
+    SkASSERT(NULL != dstColor);
+    if (NULL == inputColor) {
+        inputColor = GrGLSLOnesVecf(4);
+    }
+
+    const char *opA = lumaOpA<char>(lumaEffect.getMode(), inputColor, dstColor);
+    const char *opB = lumaOpB<char>(lumaEffect.getMode(), inputColor, dstColor);
+
+    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,
+                           opB);
+    builder->fsCodeAppendf("\t\t%s = %s * luma;\n", outputColor, opA);
+}
+
+GrGLEffect::EffectKey GrGLLumaMaskEffect::GenKey(const GrDrawEffect& drawEffect,
+                                                 const GrGLCaps&) {
+    const GrLumaMaskEffect& effect = drawEffect.castEffect<GrLumaMaskEffect>();
+    return (EffectKey)effect.getMode();
+}
+
+//////////////////////////////////////////////////////////////////////////////
+
+GrLumaMaskEffect::GrLumaMaskEffect(SkXfermode::Mode mode)
+    : fMode(mode) {
+    this->setWillReadDstColor();
+}
+
+GrLumaMaskEffect::~GrLumaMaskEffect() {
+}
+
+const GrBackendEffectFactory& GrLumaMaskEffect::getFactory() const {
+    return GrTBackendEffectFactory<GrLumaMaskEffect>::getInstance();
+}
+
+void GrLumaMaskEffect::getConstantColorComponents(GrColor*, uint32_t *validFlags) const {
+    *validFlags = 0;
+}
+
+bool GrLumaMaskEffect::onIsEqual(const GrEffect& sBase) const {
+    return fMode == CastEffect<GrLumaMaskEffect>(sBase).fMode;
+}
+
+//////////////////////////////////////////////////////////////////////////////
+
+bool SkLumaMaskXfermode::asNewEffectOrCoeff(GrContext*, GrEffectRef** effect,
+                                            Coeff*, Coeff*,
+                                            GrTexture* background) const {
+    // No background texture support.
+    if (effect && !background) {
+        *effect = GrLumaMaskEffect::Create(fMode);
+        return true;
+    }
+
+    return false;
+}
+
+#endif // SK_SUPPORT_GPU
diff --git a/src/ports/SkGlobalInitialization_chromium.cpp b/src/ports/SkGlobalInitialization_chromium.cpp
index d05af70..ebdbffb 100644
--- a/src/ports/SkGlobalInitialization_chromium.cpp
+++ b/src/ports/SkGlobalInitialization_chromium.cpp
@@ -15,6 +15,7 @@
 #include "SkLayerDrawLooper.h"
 #include "SkMallocPixelRef.h"
 #include "SkXfermode.h"
+#include "SkLumaXfermode.h"
 #include "SkMagnifierImageFilter.h"
 
 void SkFlattenable::InitializeFlattenables() {
@@ -24,6 +25,7 @@
     SK_DEFINE_FLATTENABLE_REGISTRAR_ENTRY(SkCornerPathEffect)
     SK_DEFINE_FLATTENABLE_REGISTRAR_ENTRY(SkDashPathEffect)
     SK_DEFINE_FLATTENABLE_REGISTRAR_ENTRY(SkLayerDrawLooper)
+    SK_DEFINE_FLATTENABLE_REGISTRAR_ENTRY(SkLumaMaskXfermode)
     SK_DEFINE_FLATTENABLE_REGISTRAR_ENTRY(SkMallocPixelRef)
     SK_DEFINE_FLATTENABLE_REGISTRAR_ENTRY(SkMagnifierImageFilter)
 
diff --git a/src/ports/SkGlobalInitialization_default.cpp b/src/ports/SkGlobalInitialization_default.cpp
index 24edd31..05c3c4e 100644
--- a/src/ports/SkGlobalInitialization_default.cpp
+++ b/src/ports/SkGlobalInitialization_default.cpp
@@ -46,6 +46,7 @@
 #include "SkLayerRasterizer.h"
 #include "SkLerpXfermode.h"
 #include "SkLightingImageFilter.h"
+#include "SkLumaXfermode.h"
 #include "SkMagnifierImageFilter.h"
 #include "SkMatrixConvolutionImageFilter.h"
 #include "SkMergeImageFilter.h"
@@ -86,6 +87,7 @@
     SK_DEFINE_FLATTENABLE_REGISTRAR_ENTRY(SkLayerDrawLooper)
     SK_DEFINE_FLATTENABLE_REGISTRAR_ENTRY(SkLayerRasterizer)
     SK_DEFINE_FLATTENABLE_REGISTRAR_ENTRY(SkLerpXfermode)
+    SK_DEFINE_FLATTENABLE_REGISTRAR_ENTRY(SkLumaMaskXfermode)
     SK_DEFINE_FLATTENABLE_REGISTRAR_ENTRY(SkPath1DPathEffect)
     SK_DEFINE_FLATTENABLE_REGISTRAR_ENTRY(Sk2DPathEffect)
     SK_DEFINE_FLATTENABLE_REGISTRAR_ENTRY(SkLine2DPathEffect)