Add AlphaThreshold filter.

include/effects/SkAlphaThresholdFilter.h

Index: include/effects/SkAlphaThresholdFilter.h
diff --git a/include/effects/SkAlphaThresholdFilter.h b/include/effects/SkAlphaThresholdFilter.h
new file mode 100644
index 0000000000000000000000000000000000000000..566e87575b641b0fa22e58e17c641e0dbf8cc31d
--- /dev/null
+++ b/include/effects/SkAlphaThresholdFilter.h
@@ -0,0 +1,26 @@
+/*
+ * 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.
+ */

[bsalomon, 2013/12/18 14:38:12]

New files use this copyright notice:

/*
 * Copyright 2013 Google Inc.
 *
 * Use of this source code is governed by a BSD-style license that can be
 * found in the LICENSE file.
 */

[Zachary Kuznia, 2013/12/19 01:28:40]

Done.

+
+
+#ifndef SkAlphaThresholdFilter_DEFINED
+#define SkAlphaThresholdFilter_DEFINED
+
+#include "SkRegion.h"
+#include "SkImageFilter.h"
+
+class SK_API SkAlphaThresholdFilter {
+public:
+    /**
+     * Creates an image filter that samples a region. If the sample is inside the
+     * region the alpha of the image is boosted up to a threshold value. If it is
+     * outside the region then the alpha is decreased to the threshold value.
+     * The 0,0 point of the region corresponds to the upper left corner.

[bsalomon, 2013/12/18 14:38:12]

...corresponds to the upper left corner of the src image. (?)

[Zachary Kuznia, 2013/12/19 01:28:40]

Done.

+     */
+    static SkImageFilter* Create(const SkRegion& region, SkScalar innerThreshold, SkScalar outerThreshold);
+};
+
+#endif