Add AlphaThreshold filter.

gm/imagealphathreshold.cpp

Index: gm/imagealphathreshold.cpp
diff --git a/gm/imagealphathreshold.cpp b/gm/imagealphathreshold.cpp
new file mode 100644
index 0000000000000000000000000000000000000000..2839744a7f091ff7dcd5c485937b6a5da3b07f62
--- /dev/null
+++ b/gm/imagealphathreshold.cpp
@@ -0,0 +1,82 @@
+/*
+ * 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 "SkAlphaThresholdFilter.h"
+#include "SkRandom.h"
+
+#define WIDTH 500
+#define HEIGHT 500
+
+namespace skiagm {
+
+class ImageAlphaThresholdGM : public GM {
+public:
+    ImageAlphaThresholdGM() {
+        this->setBGColor(0xFFFFFFFF);
+    }
+
+protected:
+    virtual uint32_t onGetFlags() const SK_OVERRIDE {
+        return this->INHERITED::onGetFlags() | GM::kSkipTiled_Flag;
+    }
+
+    virtual SkString onShortName() SK_OVERRIDE {
+        return SkString("imagealphathreshold");
+    }
+
+    virtual SkISize onISize() SK_OVERRIDE {
+        return make_isize(WIDTH, HEIGHT);
+    }
+
+    virtual void onDraw(SkCanvas* canvas) SK_OVERRIDE {
+        SkIRect rects[2];
+        rects[0] = SkIRect::MakeXYWH(0, 150, WIDTH, HEIGHT - 300);
+        rects[1] = SkIRect::MakeXYWH(150, 0, WIDTH - 300, HEIGHT);
+        SkRegion region;
+        region.setRects(rects, 2);
+
+        SkMatrix matrix;
+        matrix.reset();
+        matrix.setTranslate(WIDTH * .1f, HEIGHT * .1f);
+        matrix.postScale(.8, .8);
+
+        canvas->concat(matrix);
+
+        SkPaint paint;
+        paint.setImageFilter(
+            SkAlphaThresholdFilter::Create(region, 0.2f, 0.7f))->unref();
+        canvas->saveLayer(NULL, &paint);
+        paint.setAntiAlias(true);
+
+        SkPaint rect_paint;
+        rect_paint.setColor(0xFF0000FF);
+        canvas->drawRect(SkRect::MakeXYWH(0, 0, WIDTH / 2, HEIGHT / 2),
+                         rect_paint);
+        rect_paint.setColor(0xBFFF0000);
+        canvas->drawRect(SkRect::MakeXYWH(WIDTH / 2, 0, WIDTH / 2, HEIGHT / 2),
+                         rect_paint);
+        rect_paint.setColor(0x3F00FF00);
+        canvas->drawRect(SkRect::MakeXYWH(0, HEIGHT / 2, WIDTH / 2, HEIGHT / 2),
+                         rect_paint);
+        rect_paint.setColor(0x00000000);
+        canvas->drawRect(SkRect::MakeXYWH(WIDTH / 2, HEIGHT / 2, WIDTH / 2, HEIGHT / 2),
+                         rect_paint);
+
+        canvas->restore();
+    }
+
+private:
+    typedef GM INHERITED;
+};
+
+//////////////////////////////////////////////////////////////////////////////
+
+static GM* MyFactory(void*) { return new ImageAlphaThresholdGM; }
+static GMRegistry reg(MyFactory);
+
+}