Adding new benchmark to test image decoding performance.

bench/DecodingBench.cpp

+/*
+ * Copyright 2015 Google Inc.
+ *
+ * Use of this source code is governed by a BSD-style license that can be
+ * found in the LICENSE file.
+ */
+
+#include "DecodingBench.h"
+#include "SkData.h"
+#include "SkImageDecoder.h"
+#include "SkOSFile.h"
+#include "SkStream.h"
+
+/*
+ *
+ * This benchmark is designed to test the performance of image decoding.
+ * It is invoked from the nanobench.cpp file.
+ *
+ */
+DecodingBench::DecodingBench(SkString path, SkColorType colorType)
+    : fColorType(colorType)
+{
+    // Parse filename and the color type to give the benchmark a useful name
+    SkString baseName = SkOSPath::Basename(path.c_str());
+    const char* colorName;
+    switch(colorType) {
+        case kN32_SkColorType:
+            colorName = "N32";
+            break;
+        case kRGB_565_SkColorType:
+            colorName = "565";
+            break;
+        case kAlpha_8_SkColorType:
+            colorName = "Alpha8";
+            break;
+        default:
+            colorName = "Unknown";
+    }
+    fName.printf("Decode_%s_%s", baseName.c_str(), colorName);
+    
+    // Perform setup for the decode
+    SkAutoTUnref<SkData> encoded(SkData::NewFromFileName(path.c_str()));
+    fStream.reset(new SkMemoryStream(encoded));
+    fDecoder.reset(SkImageDecoder::Factory(fStream.get()));
+}
+
+const char* DecodingBench::onGetName() {
+    return fName.c_str();
+}
+
+bool DecodingBench::isSuitableFor(Backend backend) {
+    return kNonRendering_Backend == backend;
+}
+
+void DecodingBench::onDraw(const int n, SkCanvas* canvas) {
+    SkBitmap bitmap;
+    for (int i = 0; i < n; i++) {
+        fStream->rewind();
+        fDecoder->decode(fStream, &bitmap, fColorType,
+                         SkImageDecoder::kDecodePixels_Mode);
+    }
+}