Provide a GPU implementation of SkArithmeticMode

include/effects/SkArithmeticImageFilter.h

 /*
- * Copyright 2012 The Android Open Source Project
+ * Copyright 2013 The Android Open Source Project
  *
  * Use of this source code is governed by a BSD-style license that can be
  * found in the LICENSE file.
  */
 
-#ifndef SkBlendImageFilter_DEFINED
-#define SkBlendImageFilter_DEFINED
+#ifndef SkArithmeticImageFilter_DEFINED
+#define SkArithmeticImageFilter_DEFINED
 
 #include "SkImageFilter.h"
 #include "SkBitmap.h"
 
-class SK_API SkBlendImageFilter : public SkImageFilter {
+class SK_API SkArithmeticImageFilter : public SkImageFilter {
 public:
-    enum Mode {
-      kNormal_Mode,
-      kMultiply_Mode,
-      kScreen_Mode,
-      kDarken_Mode,
-      kLighten_Mode,
-    };
-    SkBlendImageFilter(Mode mode, SkImageFilter* background, SkImageFilter* foreground = NULL);
+    SkArithmeticImageFilter(SkScalar k1, SkScalar k2, SkScalar k3, SkScalar k4, SkImageFilter* background, SkImageFilter* foreground = NULL);

[reed1, 2013/05/28 16:22:02]

Add some dox, both for the k values, and for the two additional filter objects.

 
-    ~SkBlendImageFilter();
+    ~SkArithmeticImageFilter();
 
-    SK_DECLARE_PUBLIC_FLATTENABLE_DESERIALIZATION_PROCS(SkBlendImageFilter)
+    SK_DECLARE_PUBLIC_FLATTENABLE_DESERIALIZATION_PROCS(SkArithmeticImageFilter)
 
     virtual bool onFilterImage(Proxy* proxy,
                                const SkBitmap& src,
                                const SkMatrix& ctm,
                                SkBitmap* dst,
                                SkIPoint* offset) SK_OVERRIDE;
 #if SK_SUPPORT_GPU
     virtual bool canFilterImageGPU() const SK_OVERRIDE { return true; }
     virtual bool filterImageGPU(Proxy* proxy, const SkBitmap& src, SkBitmap* result) SK_OVERRIDE;
 #endif
 
 protected:
-    explicit SkBlendImageFilter(SkFlattenableReadBuffer& buffer);
+    explicit SkArithmeticImageFilter(SkFlattenableReadBuffer& buffer);
     virtual void flatten(SkFlattenableWriteBuffer&) const SK_OVERRIDE;
 
 private:
-    Mode fMode;
     typedef SkImageFilter INHERITED;
-    SkImageFilter* getBackgroundInput() { return getInput(0); }
-    SkImageFilter* getForegroundInput() { return getInput(1); }
+    SkScalar fK1, fK2, fK3, fK4;
 };
 
 #endif