Add AlphaThreshold filter.

include/effects/SkAlphaThresholdFilter.h

Index: include/effects/SkAlphaThresholdFilter.h
diff --git a/include/effects/SkMagnifierImageFilter.h b/include/effects/SkAlphaThresholdFilter.h
similarity index 53%
copy from include/effects/SkMagnifierImageFilter.h
copy to include/effects/SkAlphaThresholdFilter.h
index b5a79fa14f638c412b9c21373b0be9ac4862a8b3..3995b79bc4a3b363828aaade3f0952689c80d1f4 100644
--- a/include/effects/SkMagnifierImageFilter.h
+++ b/include/effects/SkAlphaThresholdFilter.h
@@ -1,25 +1,25 @@
 /*
- * 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 SkMagnifierImageFilter_DEFINED
-#define SkMagnifierImageFilter_DEFINED
+#ifndef SkAlphaThresholdFilter_DEFINED
+#define SkAlphaThresholdFilter_DEFINED
 
-#include "SkRect.h"
+#include "SkRegion.h"
 #include "SkImageFilter.h"
 
-class SK_API SkMagnifierImageFilter : public SkImageFilter {
+class SK_API SkAlphaThresholdFilter : public SkImageFilter {
 public:
-    SkMagnifierImageFilter(SkRect srcRect, SkScalar inset);
+    SkAlphaThresholdFilter(SkRegion region, SkScalar innerThreshold, SkScalar outerThreshold);

[bsalomon, 2013/12/16 14:20:58]

One pattern we like to use if possible in Skia is to make effects (shader, image
filter, ...) go through factory functions that return the abstract base class
rather than have public constructors on effects. If we decide later that it is
important to optimize the case where the region can be ignored then the factory
can be modified to return a bitmap shader in that case without modifying any
clients.

[Zachary Kuznia, 2013/12/18 00:06:27]

Done.

 
-    SK_DECLARE_PUBLIC_FLATTENABLE_DESERIALIZATION_PROCS(SkMagnifierImageFilter)
+    SK_DECLARE_PUBLIC_FLATTENABLE_DESERIALIZATION_PROCS(SkAlphaThresholdFilter)
 
 protected:
-    explicit SkMagnifierImageFilter(SkFlattenableReadBuffer& buffer);
+    explicit SkAlphaThresholdFilter(SkFlattenableReadBuffer& buffer);
     virtual void flatten(SkFlattenableWriteBuffer&) const SK_OVERRIDE;
 
     virtual bool onFilterImage(Proxy*, const SkBitmap& src, const SkMatrix&,
@@ -29,8 +29,9 @@ protected:
 #endif
 
 private:
-    SkRect fSrcRect;
-    SkScalar fInset;
+    SkRegion fRegion;
+    SkScalar fInnerThreshold;
+    SkScalar fOuterThreshold;
     typedef SkImageFilter INHERITED;
 };