Add benchmark for PremultiplyAlpha and UnpremultiplyAlpha in Skia

bench/PremulAndUnpremulAlphaOpsBench.cpp

Index: bench/PremulAndUnpremulAlphaOpsBench.cpp
diff --git a/bench/PremulAndUnpremulAlphaOpsBench.cpp b/bench/PremulAndUnpremulAlphaOpsBench.cpp
new file mode 100644
index 0000000000000000000000000000000000000000..f552097b60fcef32fa193d50b9ef7fc79aeba034
--- /dev/null
+++ b/bench/PremulAndUnpremulAlphaOpsBench.cpp
@@ -0,0 +1,74 @@
+
+/*
+ * 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 "SkBenchmark.h"
+#include "SkCanvas.h"
+#include "SkConfig8888.h"
+#include "SkString.h"
+
+class PremulAndUnpremulAlphaOpsBench : public SkBenchmark {
+public:
+    PremulAndUnpremulAlphaOpsBench(void* param, SkCanvas::Config8888 config)
+        : INHERITED(param) {
+        fUnPremulConfig = config;
+        fName.printf("premul_and_unpremul_alpha_%s",
+                     (config ==  SkCanvas::kRGBA_Unpremul_Config8888) ?
+                     "RGBA8888" : "Native8888");
+    }
+
+protected:
+    virtual const char* onGetName() SK_OVERRIDE {
+        return fName.c_str();
+    }
+
+    virtual void onDraw(SkCanvas* canvas) SK_OVERRIDE {
+        canvas->clear(SK_ColorBLACK);
+        SkISize size = canvas->getDeviceSize();
+
+        SkBitmap bmp1;
+        bmp1.setConfig(SkBitmap::kARGB_8888_Config, size.width(),
+                       size.height());
+        bmp1.allocPixels();
+        SkAutoLockPixels alp(bmp1);
+        uint32_t* pixels = reinterpret_cast<uint32_t*>(bmp1.getPixels());
+        for (int h = 0; h < size.height(); ++h) {
+            for (int w = 0; w < size.width(); ++w)
+                pixels[h * size.width() + w] = SkPackConfig8888(fUnPremulConfig,
+                    h & 0xFF, w & 0xFF, w & 0xFF, w & 0xFF);
+        }
+
+        SkBitmap bmp2;
+        bmp2.setConfig(SkBitmap::kARGB_8888_Config, size.width(),
+                       size.height());
+
+        static const int kLoopCount = SkBENCHLOOP(10);
+        for (int loop = 0; loop < kLoopCount; ++loop) {
+            // Unpremul -> Premul
+            canvas->writePixels(bmp1, 0, 0, fUnPremulConfig);
+            // Premul -> Unpremul
+            canvas->readPixels(&bmp2, 0, 0, fUnPremulConfig);
+        }
+    }
+
+private:
+    SkCanvas::Config8888 fUnPremulConfig;
+    SkString fName;
+    typedef SkBenchmark INHERITED;
+};
+
+static SkBenchmark* fact0(void* p) {
+    return new PremulAndUnpremulAlphaOpsBench(p,
+        SkCanvas::kRGBA_Unpremul_Config8888);
+}
+static SkBenchmark* fact1(void* p) {
+    return new PremulAndUnpremulAlphaOpsBench(p,
+        SkCanvas::kNative_Unpremul_Config8888);
+}
+
+static BenchRegistry gReg0(fact0);
+static BenchRegistry gReg1(fact1);