Add gpu implementation of SkAvoidXfermode

gm/avoidxfermode2.cpp

+/*
+ * Copyright 2016 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 "SkAvoidXfermode.h"
+
+class AvoidXfermode2GM : public skiagm::GM {
+public:
+    AvoidXfermode2GM() { }
+
+protected:
+    SkString onShortName() override {
+        return SkString("avoidxfermode2");
+    }
+
+    SkISize onISize() override { return SkISize::Make(128, 128); }
+
+    void onDraw(SkCanvas* canvas) override {
+        canvas->drawARGB(255, 0, 0, 0);
+
+        SkRect r = SkRect::MakeXYWH(32, 32, 64, 64);
+
+        SkPaint p0;
+        p0.setColor(SK_ColorGREEN);
+        p0.setAntiAlias(false);
+
+        canvas->drawRect(r, p0);
+
+        r = SkRect::MakeIWH(64, 64);
+
+        // UL corner: replace the green with a tight tolerance
+        SkPaint p1;
+        p1.setColor(SK_ColorRED);
+        p1.setXfermode(SkAvoidXfermode::Create(SK_ColorGREEN,
+                                               55,
+                                               SkAvoidXfermode::kTargetColor_Mode))->unref();
+
+        canvas->drawRect(r, p1);
+
+        r.offsetTo(64, 0.0f);
+
+        // UR corner: avoid the green with a tight tolerance
+        SkPaint p2;
+        p2.setColor(SK_ColorRED);
+        p2.setXfermode(SkAvoidXfermode::Create(SK_ColorGREEN,
+                                               200,
+                                               SkAvoidXfermode::kAvoidColor_Mode))->unref();
+
+        canvas->drawRect(r, p2);
+
+        r.offsetTo(0.0f, 64);
+
+        // LL corner: replace the green with a loose tolerance
+        SkPaint p3;
+        p3.setColor(SK_ColorRED);
+        p3.setXfermode(SkAvoidXfermode::Create(SK_ColorGREEN,
+                                               200,
+                                               SkAvoidXfermode::kTargetColor_Mode))->unref();
+
+        canvas->drawRect(r, p3);
+
+        r.offsetTo(64, 64);
+
+        // LR corner: avoid the green with a loose tolerance
+        SkPaint p4;
+        p4.setColor(SK_ColorRED);
+        p4.setXfermode(SkAvoidXfermode::Create(SK_ColorGREEN,
+                                               55,
+                                               SkAvoidXfermode::kAvoidColor_Mode))->unref();
+
+        canvas->drawRect(r, p4);
+    }
+
+private:
+    typedef GM INHERITED;
+};
+
+//////////////////////////////////////////////////////////////////////////////
+
+DEF_GM(return new AvoidXfermode2GM;)