Luminance-to-alpha color filter (SkLumaColorFilter).

include/effects/SkLumaColorFilter.h

Index: include/effects/SkLumaColorFilter.h
diff --git a/include/effects/SkLumaColorFilter.h b/include/effects/SkLumaColorFilter.h
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+++ b/include/effects/SkLumaColorFilter.h
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+/*
+ * 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 SkLumaColorFilter_DEFINED
+#define SkLumaColorFilter_DEFINED
+
+#include "SkColorFilter.h"
+
+/**
+ *  Luminance-to-alpha color filter, as defined in
+ *  http://www.w3.org/TR/SVG/masking.html#Masking
+ *  http://www.w3.org/TR/css-masking/#MaskValues
+ *
+ *  Each color is scaled by the (unpremultiplied) luminance value:
+ *
+ *  C' = [Lum * a, Lum * r, Lum * g, Lum * b]
+ *
+ */
+class SK_API SkLumaColorFilter : public SkColorFilter {
+public:
+    static SkColorFilter* Create();
+
+    virtual void filterSpan(const SkPMColor src[], int count, SkPMColor[]) const SK_OVERRIDE;
+
+#if SK_SUPPORT_GPU
+    virtual GrEffectRef* asNewEffect(GrContext*) const SK_OVERRIDE;
+#endif
+
+    SkDEVCODE(virtual void toString(SkString* str) const SK_OVERRIDE;)
+    SK_DECLARE_PUBLIC_FLATTENABLE_DESERIALIZATION_PROCS(SkLumaColorFilter)
+
+protected:
+    SkLumaColorFilter(SkFlattenableReadBuffer& buffer);
+    virtual void flatten(SkFlattenableWriteBuffer&) const SK_OVERRIDE;
+
+private:
+    SkLumaColorFilter();
+
+    typedef SkColorFilter INHERITED;
+};
+
+#endif